Absolute value of a number is the actual distance of the number from the point zero on the number line.
This means the distance of 8 from zero is 8 units to the right of zero and the distance of -8 from zero is also 8 units but to the left of zero. But both 8 and -8 have an absolute value of 8. This is because, the absolute value is distance and distance is a non-negative value.
Absolute vale of a non-negative number say 'a', is represented as |a| and its absolute value is a.
|-a| = a and |a| = a