Gerber file layers:

top-Edge_Cuts.gm1	Board outline
top-F_Cu.gtl		Component side copper
top-B_Cu.gbl		Solder side copper
top-F_Silkscreen.gto	Component side silk screen
top-B_Silkscreen.gbo	Solder size silk screen
top-F_Mask.gts		Component side solder mask
top-B_Mask.gbs		Solder side solder mask
top.drl			Drill file with plated and non plated holes. Non 
                        plated holes don't have pads.
top-top.pos             Surface mount component placement