What Makes A Cichlid A Cichlid?

[jellisict]

I know this may seem really silly but what makes a cichlid a cichlid? I have the understanding that "cichlid" is sort of a catagory in which some fish fall in to but what I dont understand is make puts them in to that catagory? is because they are really aggressive or is it because of where in the world they come from?
you might think its a silly question but im a bit of a newby and so far have just kept the little, easy-to-keep fish like tetras, so I would really appreciate it if some one would take pity and shed a bit of light on it for me, thanks.

 

[Louiseness]

Wikipedia tells me "Cichlids share a single key trait: the fusion of the lower pharyngeal bones into a single tooth-bearing structure"

Basically, it's a scientific grouping based on similar anatomical features (in this case the jaw structure). Cichlids are from the family 'Cichlidae', just like tetras are from 'Characidae' and so forth.