What exactly ' -> ' this do ??

Answer 1

The arrow operator dereferences the pointer and calls the dot operator. It's basically a short hand for this:
(*my_pointer).my_func()

Answer 2

I guess the shorthand is more like:
(*pointer).member
for
pointer->member

Answer 3

it calls the memory address of the assigned variable... like this-> a or (*this).a ... they r the same....