Developer Glossary
Plain-English definitions of programming terms — variables, functions, the DOM, promises, and more. Search, browse by topic, or jump to a letter.
48 terms total
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Terms grouped by concept area.
Programming Basics
12 terms
The vocabulary of programming
Variable
A variable is a named container for storing data that can change while your program runs.
Constant
A constant is a named value that, once set, cannot be changed while the program runs.
Data Type
A data type tells the computer what kind of value a variable holds — text, number, true/false, and so on.
String
A string is a sequence of characters — text — enclosed in quotes, like "hello" or "Ada Lovelace".
Integer
An integer is a whole number — positive, negative, or zero — with no fractional or decimal part.
Boolean
A boolean is a value that can only be true or false — used for making decisions in code.
Function
A function is a reusable block of code that performs a task, optionally taking inputs and returning a result.
Parameter
A parameter is a named placeholder in a function definition that receives a value when the function is called.
Argument
An argument is the actual value you pass into a function when you call it, filling the parameter's slot.
Array
An array is an ordered list of values stored under a single name, accessed by their position (index).
Loop
A loop is a construct that repeats a block of code multiple times, either a fixed number or until a condition is met.
Scope
Scope is the region of your program where a variable is visible and can be used.
Web Development
10 terms
The vocabulary of the web
HTML
HTML (HyperText Markup Language) is the standard language used to structure the content of web pages.
CSS
CSS (Cascading Style Sheets) is the language used to style and lay out HTML content on a web page.
DOM
The DOM (Document Object Model) is a tree-like representation of an HTML document that JavaScript can read and modify.
Element
An HTML element is a piece of a web page defined by a start tag, content, and an end tag, like <p>Hello</p>.
Attribute
An HTML attribute is a name-value pair on an element tag that configures or adds extra information to it.
Selector
A CSS selector is a pattern that matches one or more HTML elements so you can apply styles to them.
Class (HTML)
The class attribute assigns a label to an HTML element so it can be styled or selected together with others.
ID (HTML)
The id attribute gives an HTML element a unique identifier on the page, used for styling, scripting, and anchoring.
HTTP
HTTP (HyperText Transfer Protocol) is the set of rules browsers and servers use to request and send web resources.
URL
A URL (Uniform Resource Locator) is the address that identifies a specific resource on the web.
JavaScript Basics
10 terms
The vocabulary of JavaScript
JavaScript
JavaScript is the programming language that runs in web browsers to make web pages interactive and dynamic.
Callback
A callback is a function passed into another function as an argument, to be called later when something happens.
Event
An event is a signal the browser sends when something happens — a click, a key press, a page load, and so on.
Event Listener
An event listener is a function registered to run when a specific event occurs on a specific element.
Object
An object is a collection of key-value pairs that groups related data and functions under a single name.
Promise
A promise is an object representing the eventual result of an asynchronous operation — success or failure.
async
The async keyword declares a function that always returns a promise, enabling await inside it.
await
The await keyword pauses an async function until a promise settles, then resumes with the resolved value.
Module
A module is a self-contained file of code that can export values and import them from other modules.
Expression
An expression is any piece of code that evaluates to a single value, like 2 + 3 or "Hi, " + name.
Git Basics
8 terms
The vocabulary of version control
Repository
A repository (repo) is a folder Git tracks — it stores your project's files and the full history of changes.
Commit
A commit is a snapshot of your project's files at a moment in time, saved to the repository history.
Branch
A branch is an independent line of development that lets you work on changes without affecting the main history.
Merge
Merging combines the changes from one branch into another, uniting two lines of development.
Clone
Cloning downloads a remote repository to your local machine, including its full history and remote link.
Remote
A remote is a named reference to a repository hosted elsewhere (e.g. on GitHub) that you can push to and pull from.
Push
Pushing uploads your local commits to a remote repository so others can see and pull them.
Pull
Pulling downloads commits from a remote repository and merges them into your current local branch.
Python Basics
8 terms
The vocabulary of Python
Python
Python is a high-level, readable programming language known for its simple syntax and broad use.
List
A list is an ordered, mutable collection of items in Python, written as [1, 2, 3].
Tuple
A tuple is an ordered, immutable collection of items in Python, written as (1, 2, 3).
Dictionary
A dictionary is a collection of key-value pairs in Python, written as {"key": value}, for fast lookups by key.
Python Module
A module is a .py file containing Python code that can be imported and reused in other files.
Package
A package is a folder of Python modules with an __init__.py file, letting you import them as a group.
Exception
An exception is an error that occurs while your program runs, which you can catch and handle with try/except.
Indentation
Indentation is the leading whitespace before a line of code. In Python, it defines code blocks instead of braces.
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