Absolute value describes the distance of a number on the number line from 0 without considering which direction from zero the number lies. The absolute value of a number is never negative.
6 is 6 away from zero, so the absolute value of 6 is 6
-6 is 6 away from zero, so the absolute value of -6 is 6
in other words it is the magnitude of a number, no negatives allowed.