OS X V10.7 Lion :: Icons On Docking Station?

I would like to do some house keeping of icons on the docking station.  There are some icons that I use them less often and I would like to pick it up from the Applications Folder on the right side.  I want to remove icons that used for less often and add new icons for frequent use.  Can someone point me to the place where has worked instructions doing the following.

1.  I notice there are two parts of icons: one on the right and others on the left.  What is the defination of these icons?

2.How can I create the new icon of application and add icons to the docking station for frequent use?

3.  How can I restore the icons that I removed?

Info:
iPad 2, iOS 5.1.1