Gerber file layers:

top-Edge_Cuts.gko	Board outline
top-F_Cu.gtl		Component side copper
top-B_Cu.gbl		Solder side copper
top-F_SilkS.gto		Component side silk screen
top-B_SilkS.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 plated through holes
top-NPTH.drl		Drill file non plated through holes