In fact, after you open the file with CAM350, the name inside is given by the operator himself, but there is a default standard in this industry.

TOP is the top floor (some factories are called L 1).

BOT is the bottom circuit layer (some factories are called L2).

Plate is the appearance layer of the product.

GTS top solder mask layer (also called top window layer)

GBS bottom solder mask layer (also called bottom window layer)

Top character layer of GTO

GBO bottom character layer

DRL is drilling.

Flexibility is a kind of wrapping paper (also called tribute tape)

If it is a flexible board, there are also strengthening layers, bending areas and so on.

What's more, if you just learn CAM, I suggest learning genflex, which is much more powerful than CAM350!