Ex1+T1+Question+2

Yesterday I found out this code. I want to know in general what it is used for. Also when trying to compile it there were several error. Find all the errors and correct the code so it can be used.
int a ; float b ; Double d3 = 0 ; String s ; char c ; a = Int32.Parse(textBox1.Text) ; b = Int32.Parse(label1.Text) ; if ( a > b ) { d3 = a + b ; } if ( d3 == 0 ) { textBox1.Text="" + (d3 + b); } else { MessageBox.Show ("No es....." + b) ; } if ( a == b ) { MessageBox.Show ("Obvio el número es....") ; } else { MessageBox.Show ("DUH, el problema con tus números es que....."); } c = Int32.Parse(textBox1.Text) ; s = a + b + ("hola");