What is a bookmark and how do I use it?

[pickupthismess]

The subject title says it all

what on the web?

When you are on a page you like and think you might want to remember/ refer back to, you bookmark it. Then you can open the bookmarks menu and find it again if you want to go back to it. Et voila!

So how does it differ from favourites?

It doesn't really - Favourites is just IE's name for bookmarks.
I use Google bookmarks because I find it's the easiest way to get them on any computer I'm using

Aah I see. Where is the book marks menu? DO you have to be signed in to google?

It's part of Google toolbar, and to use the bookmarks you need a Google account (which is not the same thing as a Googlemail account)
Do you use IE or Firefox? - I can give you a link to the right toolbar download.