When you use ///, it will generate comments based on the function header (as you see in your example), which can then be referenced when you use the function elsewhere. For example, if I had the following:
///<summary>
///Does cool things
///</summary>
///<param name="x">A cool number</param>
//There's another for return, I don't remember the exact format:
///<return>A frigid number</return>
int function(int x)
If I were to write this somewhere else:
int a = function(b);
I can put my mouse over "function" and a little window will pop up, with a summary that it does cool things and explaining that it takes a cool number and returns a frigid one. This will also work for overloads, so you can scroll through each overload header and put different summaries/variable explanations on all of them.