Answer 1

Modulus is... this: %
It's the percentage symbol, yes, but it is used to display remainders from divisions.

So example time:

2 % 10 will = 0 , because there's no remainder. But...
2 % 11 will = 1 , because there was a remainder of 1 left.

The modulus operator appears in Most Programming Languages, being useful to help determine odd or even numbers.