Gear Motor
"Gear motor" refers to a combination of a motor plus a reduction geartrain. These are often conveniently packaged together in one unit. The gear reduction (gear train) reduces the speed of the motor, with a a corresponding increase in torque. Gear ratio range from just a few (e.g. 8) to huge (e.g. 500). A small ratio can be accomplished with a single gear pair, while a large ratio requires a series of gear reduction steps and thus more gears. There are a lot of different kinds of gear reduction.
In the case of a small transmission ratio N, the unit may be backdrivable, meaning you can turn the output shaft, perhaps by hand, at angular velocity w and cause the motor to rotate at Nw. A larger transmission ratio N may make the unit non-backdrivable. Each has advantages for different circumstances. Backdrivability depends not just on N, but on may other factors.
