game development - with Renderware

I know everything about software development. However, I wanted to know about the game development - the arts, the programming etc. To make it clearer what I'm asking for I'll tell you what I do know and you can fill in the rest: the artists use Maya/Lightwave/3DS etc to create and design the models - the characters, the buildings ,the streets and terrains etc These are imported into the game engine format. The programmers hack away at the code to make it do what the artists want it to do and to make it more efficient etc. Now my big question is - what role does Renderware perform in all this supposing it's being used ? It isn't an engine so what does it actually do and why can't the game designers simply use the game engine without using Renderware ? thanks