Vertical Battery Grip for DSLR Cameras - Buying Guide

I have been hanging around in camera accessories, and many times I see photographers asking the question "Do I need a camera battery grip/holder?" or "What hand grips are used for?".  So I decided to write this blog post in order to answer this question. Let's start by saying that if you ask yourself  if you need a battery grip, then you probably have to read this buying guide to found out. But