Generator/alternator
An electric motor converts electrical energy into mechanical energy, whereas a generator (alternator) converts mechanical energy into electrical energy. In its simplest form, a motor is operated at nominal speed to generate electrical energy.
Application:
Combustion engine + alternator = generator of electricity
Rotary-current motor + D-generator = converter
There is the same variety of generators, as there are motors:
DC motor DC generator
AC motor AC generator
D asynchronous motor D asynchronous generator
D synchronous motor D synchronous generator
in self-excited and separately excited versions, but also with permanent excitation by a permanent magnet.
(D = three-phase current)