I am currently trying to learn C#, and I ran across following question:
What is the difference between
[,] form creates rectangular two dimensional array. When you specify the dimensions you will get a two dimensional matrix of those sizes. All its elements are initialized to the default value of the element type.
int[,] array = new int[4, 2];
 is called jagged array and it is basically an array of arrays. When you create it, you first only specify the size of the first dimension:
int jaggedArray = new int;
Now you have to create a
new array for each of the rows manually (they are initially
jaggedArray = new int; jaggedArray = new int;
The advantage of this is that each row can have a different length.