The drum contains the snake and keeps it from tangling, making it more manageable to store and use.
Drum auger handle and handhold
The purpose of the turning handle on the drum auger is to rotate the snake. Although there are versions which automatically feed the snake out, these are rarer.
The handhold steadies the auger as you use it.
Drum auger stop / start mechanism
The user is usually required to pull the snake out by hand.
The stop/ start screw on the drum auger (which varies from model to model) allows you to control how much of the snake is released at a time.
Drum auger power drill attachment
Sometimes there will be a place on the back of a drum auger for a power drill to be attached. A drill can be used on a low setting to rotate the snake.
The drill is slotted onto the attachment and then tightened, as you would with a drill bit.