Hi Neelima
Welcome to SCN.
The queries you asked are frequently asked and answered in this forum. Since you are new to SCN, I'd recommend reading up the blog below on the searching capabilities in SCN. With that, it's possible to get answers to your questions even before opening a thread. (I personally prefer using the custom Google search for SCN)
Everything I know about... Searching SCN
Rgds
Eng Swee