Apps and What Software Really Is

"Software," "app," "program," "application" — these four words get thrown around as if they were different things, and the result is quiet confusion. The truth is simpler than the vocabulary makes it look, and this topic ties the chapter together by saying what each one actually means.

Software is the set of instructions that tell a computer what to do. The physical machine — the parts you could touch, the CPU and memory and disk from Chapter 1 — is the hardware. Software is everything the hardware runs: the operating system, your browser, the photo editor, the game. One is the body; the other is what the body does.

Software vs Hardware

A music player makes the split easy to feel. The device — the speaker, the screen, the buttons — is the hardware. The songs are the software. The player is useless with no music to play, and the music does nothing without a player to run it. Each needs the other, and neither is the other.

The reason this matters is that the two can change independently. You can swap the songs without touching the device, and you can move the same songs to a new device. Software is the same: the instructions can be replaced, updated, or copied to another machine, while the hardware sits unchanged. That's the analogy's whole job — to make that separation obvious — and from here we'll just say software and hardware.

App, Program, Application — Mostly One Thing

App, program, and application are, for practical purposes, the same word. All three name a single piece of software built to do a particular job — write a document, edit a photo, browse the web. The differences are only habit and setting, not substance.

"Application" is the formal term. "Program" is the older, more general one — often used for anything a computer runs. "App" is the short, casual version that stuck to phones first and then spread everywhere. When someone says "open the app," "run the program," or "launch the application," they mean the same act: start a piece of software so the computer begins following its instructions.

Where Software Lives

Here is the split that opens the rest of the course. Some software lives on your own device — installed onto your storage, run by your own CPU. A photo editor or a game keeps working with the internet switched off, because everything it needs is already on the machine in front of you.

Other software lives on a server — a computer that runs all the time in a data center, which you reach over the internet. When you open a website, the software that builds that page isn't on your device at all; it runs on the server, and your browser just shows what the server sends back. The same goes for a web app like online email or a maps site.

This is the bridge into Part 2. "Turning on a computer," the thread of the first three chapters, was all about software on your own machine. "Opening a website" — opening example.com, the thread that carries the rest of the course — is about software running somewhere else, reached across a network. Everything ahead builds on that one idea.

Why Software Can Be Updated

Because software is just instructions stored as files, it can be changed by replacing those files. That is all an update is: newer versions of the software's files swapped in for the old ones, fixing problems or adding features. The hardware never moves.

This is also why software on a server can improve without you doing anything. The people who run the server replace the files on their end, and the next time you open the site you get the newer version automatically — no download, no install on your side. Software on your own device, by contrast, updates only when its files on your machine are replaced, which is why those apps ask you to download and install.