Information onOO ABAP

Hi Experts,

This is siri,I am ABAP Fresher. Please can any one provide me the information regarding OOABAP.

1) What is OO ABAP.?

2) How to start it from starting?

3) Where to find all predeifined methods and classes?

4) How to use exactly those prdefined methode and classes?

Please help me out for sharing the your valuable information..

Thanks in Advance.

Thanks and Regards

Siri..