Abs

Explanation
An absolute value of a number is defined as this number without a sign. That means that absolute value of any positive number equals to this number, while an absolute value of a negative number is a number without a ´minus´ sign. To be complete, the absolute value of 0 is 0.

Examples
Suppose the argument is 5, then abs(5) will return 5.

Suppose the argument is -5, then abs(-5) will also return 5.