A monkey was a member of a wide variety of primates, most of which were native to the planet Earth, which were part of the simian family. Monkeys were not technically apes, although they were often referred to as such, just as apes were likewise incorrectly referred to as monkeys.
Exxorian monkeys were very similar to Earth monkeys, except they were different, in that they seemed to be biologically monotreme, as they apparently gave birth to their young by laying eggs.
Another type of monkey was the baboon. The Egyptian god known as Thoth had the appearance of that type of monkey.