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Builder Glossary
Plain-English definitions of the terms that come up across every RadarTrek course — Git, SQL, the web, JavaScript, React, APIs, and Docker. Each one links straight to the lesson that actually teaches it, not just a dictionary entry.
Programming Foundations
A named container that holds a value your program can read and change.
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Code that runs different instructions depending on whether something is true or false.
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Code that repeats an action automatically, instead of writing it out by hand each time.
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Web Fundamentals
The system that translates human-readable domain names into the IP addresses computers use.
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The protocol browsers and servers use to request and send data over the web.
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The service that keeps your website's files and code running on a server, reachable 24/7.
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HTML & CSS
A piece of structured content on a page, marked up with an opening and closing tag.
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The pattern that tells CSS which HTML elements a style rule should apply to.
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The rules that determine how an element's content, padding, border, and margin take up space.
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JavaScript
A reusable block of code that takes input, does something, and can return a result.
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The browser's live, in-memory tree representation of an HTML page that JavaScript can change.
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JavaScript syntax for writing code that waits on slow operations — like network requests — without blocking everything else.
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React
A syntax that lets you write HTML-like markup directly inside JavaScript.
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A self-contained, reusable piece of UI defined as a JavaScript function that returns markup.
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Data passed from a parent component into a child component, like arguments into a function.
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Data a component manages itself and that changes over time, triggering a re-render when updated.
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Databases & SQL
The unique identifier that makes every row in a table distinct.
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A column that links one table's row to another table's primary key.
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The SQL clause that combines rows from two or more tables based on a related column.
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Buckets rows into groups so aggregate functions can summarise each group separately.
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A structured system for storing, organising, and retrieving information reliably and fast.
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APIs
A defined way for one piece of software to request data or actions from another.
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A widely-used convention for designing APIs around resources and standard HTTP methods.
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A specific URL an API exposes for performing one particular action.
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Git & GitHub
A saved, permanent snapshot of your entire project at one point in time.
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A project folder tracked by Git, containing the full history of every commit.
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An isolated, parallel version of your project where you can work without affecting the main code.
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A GitHub feature for proposing that one branch be merged into another, with room for review.
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What happens when two branches change the same line of the same file in different ways.
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DevOps & Docker
A lightweight, isolated package that bundles your app with everything it needs to run, anywhere.
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A text file with step-by-step instructions for building a Docker image.
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Automatically testing and deploying code every time it changes, instead of doing it by hand.
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AI & LLMs
The small chunk of text — roughly 3-4 characters — that an LLM actually reads and bills you for.
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The maximum number of tokens an LLM can hold in view at once — input and output combined.
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The setting that controls how predictable vs. varied an LLM's next-word choices are.
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The standing instructions that set an LLM's persona, rules, and constraints for an entire conversation.
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When an LLM states something false with full confidence, because it predicts plausible text, not retrieves facts.
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A numeric vector that represents what a piece of text means, placing similar meanings near each other.
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A database built to store embeddings and quickly find the ones most similar to a query vector.
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Retrieval-Augmented Generation — giving an LLM your own documents to read before it answers.
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Further training a model on your own examples to change its style or format, not to teach it new facts.
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Showing an LLM a few labelled examples in the prompt instead of describing what you want in prose.
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Malicious instructions hidden in content an AI processes, designed to override its original task.
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An LLM that can take actions, observe the results, and repeat — instead of answering in one shot.
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Giving an LLM a defined set of functions it can request to call, so it can act, not just respond with text.
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SaaS & Business
Monthly Recurring Revenue — the predictable subscription revenue a SaaS business collects every month.
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The percentage of customers (or revenue) a SaaS business loses to cancellations in a given period.
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Customer Acquisition Cost — the fully-loaded cost of acquiring one new paying customer.
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Lifetime Value — the total revenue you expect a customer to generate before they churn.
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A free, permanently-usable tier designed to convert a portion of users to paid plans over time.
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Minimum Viable Product — the smallest version of a product that lets one real customer solve one real problem.
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How many months a business can keep operating before it runs out of cash, at its current burn rate.
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Security
A vulnerability where attacker-controlled input runs as script in another user's browser.
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A vulnerability where attacker input is interpreted as part of a database query instead of as data.
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An attack that tricks a logged-in user's browser into submitting a request they never intended to make.
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A protocol that lets a user grant an app limited access to their account on another service, without sharing their password.
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A signed, self-contained token that carries identity claims and can be verified without a database lookup.
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System Design
A component that spreads incoming requests across multiple servers instead of sending them all to one.
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Handling more load by adding more servers, rather than making one server bigger.
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Storing the result of an expensive operation so the next request gets it instantly instead of redoing the work.
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CI/CD
Accessibility
GraphQL
A request that asks a GraphQL API for exactly the fields you need, in one round trip.
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The GraphQL operation type used to create, update, or delete data, as opposed to just reading it.
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The function that actually fetches or computes the data for one field in a GraphQL schema.
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Marketing
The percentage of people who saw your ad or link and actually clicked it.
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How much you pay, on average, each time someone clicks your ad.
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A link from another website pointing to yours — the strongest SEO ranking signal you can't directly control.
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A pre-written series of emails sent automatically on a schedule after someone takes an action, like signing up.
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Learn it properly
Definitions are step one. Courses are step two.
Every term here links to a free lesson in the matching RadarTrek course — start with the foundations track if you're new to building.
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