An electric device which rotates(or in some way moves) when current is applied.
There are many types of motor:
They generally consist of a minimum of a moving section (rotor) and a static (stator) section. One or both of which has an Electro Magnet, and the other may or may not contain permenant magnets.
One important consideration when using any motor is its Torque as well is its Electrical Current and Electrical Voltage requirements.
Time to build your own robot! Using a Raspberry Pi with parts and some time, you can use my book to learn how to make and program a robot with automatic behaviours.