When do i use a pointer and why?

Answer 1

Pointers can be useful in efficient data structures such as linked lists, binary trees, etc.

Sample:
http://www.cprogramming.com/tutorial/lesson18.html

Answer 2

This question is mentioned several timez.
https://www.sololearn.com/discuss/122211/?ref=app
https://www.sololearn.com/discuss/514500/?ref=app
...

Answer 3

For Dynamic memory allocation pointer is used