A visual guide for non-technical people
Every website or app starts as a collection of files on someone's computer. These files contain the code, images, and content that make up what you see on screen. Think of them like documents in folders, just organized in a way that browsers and servers understand.
When files only live on your computer, only you can work with them. To let other people use them, those files need to be served by a machine they can reach.
A local server is a program running on your computer that acts like a small private website. It reads your files and serves them to your browser, so you can test a real page before anything is public.
The address localhost means “this computer.” When you visit localhost:3000, your browser is talking to your own machine, not to the public internet.
Deploying means copying your files from your computer to a remote server, a machine on the internet that stays online so other people can reach it. The public version changes only after that handoff finishes.
Deployment usually runs through a short pipeline so broken changes do not go live immediately. That extra delay is what makes remote systems safer than just saving a file.
That is the full journey: files on your computer, previewed by a local server, then deployed to a remote server for other people to use.