Eagle Layers

Layers in Gerber

Number	Name	Descrpition
1	Top	topper copper trace
2-15	Middle	On multi-layer boards with the professional version of Eagle, you also have access to layers 2-15
16	Bottom	bottom copper trace
17	Pads	Normal pads for PTH components (Parts through holes)
18	Vias	Example (For lines goes from bottom to top or vice verse, help you draw lines easy)
19	Unrouted	unrouted airwires
20	Dimension	draw the outline of your PCB on this layer, help the manufacturer to cut it easily, without this outline, it's can't be made.
21	tPlace	is used to draw lines that will be rendered as the silk screen on your PCBs
22	bPlace	-
23	tOrigins	-
24	bOrigins	-
25	tNames	is used to hold the unique 'names' for each part on your PCB (ex. C1, R5, X12, etc.)
26	bNames	-
27	tValues	is used to hold the value for each part (such as 10K, 0.1µF, AT86RF212, etc.)
28	bValues	-
51	tDocu	is used for documentation purposes, such as drawing the mechanical dimensions of your part (more on that shortly!). Normally this layer isn't printed on the PCBs, but it's very important for documentation and for PCB design.

use script for each design project
copy and edit mycolor.scr, edit your own color, color number 0 is white in color palette, and same for the rest

All has to be closed loop