which situation abstract class i should use

Question

Possible Duplicates:
What is the purpose of abstract classes?
When to use interfaces or abstract classes? When to use both?

Hi ,

Am not worked on extream level of oops in my projects ,

So i have little doubts ,

In which situation should i use abstract method or classes ,

Basically i know about abstract class definition and flow,

I got details from this URL

Doubt is which situation should i use abstract class and methods ,