Let's take the simple example of a blog with:
- A post
habtm
tags - A tag
habtm
posts
[based on a true story]
So. Your friend's about to teach you how to make a website. Great!
You make a file, and you save it as 'index.html'. Why it's called 'index' isn't really explained to you, but whatever.
You type the following.
hello world