Providing help for users in web applications, as well as any other application, is important to get right. And with the freedom you have as designer or developer to create your own concept, even more and better help is required if you want your users to understand what they can do, what they should do and how to achieve that.
At the same time, it has to be a no-hassle operation to find and learn from help pages for a web application. How can you do that?
Context-Sensitive Help
The definition of Context-Sensitive Help, from Wikipedia goes like this:
“Context-sensitive help is a kind of online help that is obtained from a specific point in the state of the software, providing help for the situation that is associated with that state.
Context-sensitive help, as opposed to general online help or online manuals, doesn't need to be accessible for reading as a whole. Each topic is supposed to describe extensively one state, situation, or feature of the software.”
It doesn’t have to be difficult, advanced or anything like that. Rich tootips works very well. If something can’t be explained inside a rich tooltip, add a “Read more” link that opens in a new window.
Take a look at some inspiration from a Smashing Magazine article:

Google Reader, that is.

And that was TasteBook

Flashden.net