[sdiy] Is there a standard set of Gerber files?

[David Ingebretsen]

I'm just curious if there is a standard set of Gerber files to send to a PCB
shop? Eagle has a lot of layers, most of which I don't use in my layouts.
So, I'm curious about PCB shops which require Gerber files. Is there is a
standard set of Eagle layers I should export? Should I combine some layers,
like top copper/pads/vias or should they all be separate?

Thanks
David