Apps, websites, and programs

What's the difference, really? And why does it matter for what we're about to build?

These words get tossed around like they all mean the same thing. They don't — quite. The differences are small but worth knowing, because Claude Code is going to help you build all three.

Program

The most general word. A programis any set of instructions that runs on a computer. The thing reading the time from your computer's clock is a program. Microsoft Word is a program. The web browser you're reading this in is a program. Claude Code is a program.

If it's software that does something when you start it, it's a program. The word doesn't say anything about size, interface, or how you interact with it.

App

An app (short for application) is a program with a user interface, designed for a specific job. Spotify is an app — it plays music. Your camera is an app — it takes pictures. A calculator is an app — it does math.

Apps almost always have a window, icons, buttons. They're built to be friendly. You install them, click their icon, use them, close them.

Note

"App" got popular with smartphones, but desktop programs with interfaces (Word, Excel, Photoshop) are also apps. The terms have basically merged. A program with a window and a purpose is an app.

Website

A websiteis a set of pages that live on a server and that you view through a web browser. You don't install a website. You just visit it — type a URL or click a link, and your browser fetches the pages from the server and shows them to you.

Some websites are simple (an "about me" page). Some are enormous (Amazon, Wikipedia, Google). The size doesn't change the category — if it lives in a browser at a URL, it's a website.

Web app

A web appis the blurry middle ground. It's a website that behaves like an app — interactive, with logins, buttons, real-time updates, saving your work. Google Docs is a web app. Gmail is a web app. Figma is a web app. This site you're on is a small web app.

From a user's perspective the difference between a regular app and a web app is mostly: do I have to install it? A web app you just open in a browser. An app you install on your machine.

Script

A scriptis a small program, usually written in a single file, designed to do one specific job and then exit. Think: "rename all the photos in this folder," or "download every PDF linked on this page."

Scripts don't usually have a graphical interface. You run them from the terminal, they do the thing, they finish. Most of the work Claude Code does on your behalf when you ask it to "process these files" is writing a script and running it.

Server / service / API

A serveris a program that runs in the background and answers requests. You don't click on it; other programs talk to it over the network. The Spotify app on your phone is the client; somewhere there's a Spotify server answering "what song does this user want next?"

When someone says API(Application Programming Interface), they usually mean the menu of requests a server is willing to answer. "Hit the Spotify API to get the user's playlists." You'll meet APIs constantly once you start building things.

Why this matters

Claude Code is itself a program — specifically, an app that runs in your terminal. Underneath, it talks to a server (Anthropic's) via an API. When you ask Claude Code to build something for you, it might be writing a script, a website, a web app, or all three. Knowing the words helps you describe what you want.

What to take with you

Program — any software that runs.
App — a program with an interface, built for a job.
Website — pages on a server, viewed in a browser.
Web app — a website that acts like an app.
Script — a small program that does one job from the terminal.
Server / API — a program that answers requests from other programs.