Can someone please help me? I have trouble finding were the masks are on lascaux. ...if there are any...help.

There is one mask, on the left-hand side under the Paper section. There is a big box that says "Mask Off." If you right click on it, you can set the mask color to the current color. Left click rotates between mask off/on/reverse.
However, there are a number of tools that make masks less useful, such as using multiple layers, selections, and the "behind" brush mode.
I only use masks if I feel like staying on one layer, or am nostalgic for paintbbs.

Thankyou. I must admit though, I'm still a little confused. But that really helped.

i actually like the way you can convert a sketch with a sharp edged brush back into a multi-layered image using mask and erase, since i usually edit stuff several times. not sure what else to use it for since i use layers the rest of the time.