stacking/layering samples...

call me silly, but my usage with the MPC2XL has not expanded much in the sampling department and I would love to make that jump so......this may be a bonehead question, but what is this term of layering samples so commonly used referring to exactly? I have an idea but would love more clarity. If anyone could give a hypothetical synopsis (brief) to explain, would love that.....
ThanX

well basically on the program assign screen (shift 6 i believe) on the bottom where it says normal you can set it to simult and have that same pad also trigger up to 2 more sounds (that are already assigned to other pads). so you can have pad 3 also play pad 4 at the same time everytime you hit pad3.

from there you can get creative with it and have the attack rolled off on one of the sounds and the decay rolled off on another so you kinda 'morph' the sounds together everytime you hit the pad.
morph isnt the right word, but try it out with 2 different sounding snares or kicks or whatever you want.

you can also stack 2 versions of the same kick where one is normal and one is tuned down an octave (-120) and maybe filtered down some.

in simple terms that clears up a lot. Was concerned I wouldn't get any feedback on that one...