Telling the Difference
Typically, the difference between monkeys and apes is that monkeys are generally smaller with longer tails, whereas apes are usually much larger and tend to have very stunted tails, if any at all. The Lion King's Rafiki, in fact a mandrill and not a baboon, should actually have a much shorter tail!
Monkeys include species such as tamarins, spider monkeys, howler monkeys, baboons and macaques, which all exhibit the characteristic long tail.
Some monkeys are able to use their long tail as a fifth limb. These tend to be those that tend to live up in the tree canopy, like the spider monkey, whose tail can support the weight of his entire body. Perhaps it's this trait which has led to spider monkeys being used in films more than any other monkey.
Howler monkeys are very well-named. They are one of the loudest animals on the planet and their howl can be heard as far as 10 miles away!
Another notable group of monkeys, macaques, are the most northernly of all the primates (except for humans, of course). They can be found on the island of Gibraltar and lazing in the hot springs of Japan.
Examples of apes include chimpanzees, gorillas, orang-utans, gibbons and humans.
Orang-utans aren't named because of their orange colouration, as you may have first thought. The word "orang-utan" is actually Malay for "man of the forest".
A yawning primate most often means that they are either tired or livid, something you probably don't want to mistake. Similarly, grinning or pulling a lip is a sign of aggression, along with head bobbing and jerking the head and shoulders forward. That's why smiling (essentially, baring your teeth) at primates in zoos is discouraged as it can be a sign of aggression.
Both apes and monkeys show exceptional intelligence in their tool use, with chimpanzees taking the crown (not counting us humans). They are able to use sticks to fish for insects and crack nuts with stones or logs, showing incredible ingenuity.
Apes and monkeys can both catch colds, just like humans. Primates can also sometimes catch other diseases from humans too, and as such it is important to be careful when coming into contact with them in the wild.
However, they are perhaps not as intelligent as some people thought during the Napoleonic Wars. A shipwrecked monkey once washed ashore in Hartlepool, whereupon it was arrested and put on trial for being a French spy. After being found guilty, the monkey was hanged from the mast of a fishing boat. The term "Monkey Hangers" is still attributed to people from Hartlepool. Also, a monkey was tried and convicted for smoking a cigarette in Indiana in 1924!