That is way, way too much to explain here!
There are three things you can do:
1) Look at MSDN: they give a reasonable explanation of each event.
http://msdn.microsoft.com/en-us/library/system.web.ui.webcontrols.gridview_events.aspx[
^]
2) Look in your course book, and see if that explains them - since it can give pictures and is written by a proffessional writer, it should be able to do a better job than we can.
3) Go talk to your tutor - he or she should be able to explain them to you in terms that should be understood given your experience level (which we don't even know!)