Hoppers / Loaders
Paintballs can be loaded one at a time by hand, but it's much more efficient to have lots of paintballs waiting to fall in by themselves. Some hoppers simply hold balls and let gravity do the work while others considerably speed things up.
What's the difference between gravity fed and motorized hoppers?
Gravity fed hoppers are simply containers that hold paintballs while motorized hoppers physically help feed paintballs into a paintball gun.