Welcome to Android Forums.
For starters, You might find the links in my signature line (right below the friendly "Don't Panic"
) helpful. There's some good basic Android info there.
Also, here's a couple of links that should help explain rooting:
General Android phone FAQ (updated 9th October 2012)
(See section 3.1 - What is ‘Rooting’, and is it for me?)
Rooting Best Practices
Finally, here's a link to your phone's section here at AF, where you'll find all sorts a valuable info specific to the SGS2.
I hope that helps, and just let us know if you have any other questions.