In c# in declaring variables and performing operation

In c# in declaring variables and performing operation

I am eager to learn windows application development,so i am learning c#.I
have a doubt that when we are declaring integer variable still we using
int.parse() method to perform action.Can anyone help me in this,also i am
learning using channel9 videos,still i need to be more expert so i can
easily learn windows app development,suggest me some websites,Thanks also
suggest me for windows app development Thanks to all