so, frequently people will conflate monkeys and apes, and use the terms interchangably (that's the left end of the graph), people with a bit more knowledge may be aware of the common definition that monkeys have tails while apes do not (that's the middle part), while those with more knowledge of biological taxonomy argue that, since new world monkeys and old world monkeys share a more distant common ancestor than old world monkeys and apes, if we want to define a term 'monkey' that encompasses both new and old world monkeys, it would have to also include all apes (including humans). so, according to the right side of the graph people, chimpanzees are apes are monkeys (though lots of monkeys are not apes, it's a squares and rectangles kinda thing).