When would you use a pointer? A reference?

I would suggest not to use pointer. Better use references. As the pointer is likely to complicate the process.

they are used very less

It was used to identify the memory location.

There are other OOPS concepts which can be used in place of pointers, if you wish to avoid them.

Well, if I want to use some data types value referring to other then I simply use pointer. We can do the same with other method too.. More use of pointer is not good.

pointers make your program more efficient but they also make your program slow

Pointer are used less. It makes your program little tough. It is better to use object. Always try to keep your program simple. The chances of error will be less.
Pointers are mostly used to identify location in the memory to store value

Actually pointers are used to identify the memory location of a particular data where it is stored.
Pointers are used by the hackers in hacking or identifying a particular IP address.