What does ref keyword stands for?

Answer 1

ref is short for "reference" it just implies that changes to that variable in the scope of the method will also effect the value of the argument in the scope the method was called from. Pass by value is the default in which case you only get the value instead of a reference to the arguments.

Answer 2

in short, in pass by ref the passed parameter holds the same memory location as it was in main function.