A drain auger or snake is a mechanical tool for unclogging drains. They consist of a long spring tipped with a point which is fed down the drain and then wound into the obstruction. Off-the-shelf models come in two varieties (whose names I have fabricated):

The spring coils up into a circular container when not in use. The crank is usually on the top of this container and the spring feeds out through the bottom. These are neat, general-purpose, and come in significant lengths.
The spring is straight and slides back and forth through a pipe. These are primarily designed for short distances via drain traps. In particular, toliets.

The most popular professional models are manufactured by Roto-Rooter Corporation. They even make electic augers. Their name is close to synonymous with the device itself.