Okay, I have been creating objects, resizing, scaling and stuff but i haven't really bothered yet to know what the numbers are measuring at.

For example, i create a cube and scale it up to 2,2,2 for xyz

does the 2 stand for 2 inch? feet? cem? or etc.?
or does it not really matter?

One more question? what's the ideal size when creating something? or will it not matter because you can always use zoom?

thanks!