Answer:
The difference in meaning is that
-3 is a signed value. It lies to the left of zero
+3 is also a signed value, and since it is positive, it lies to the right of zero
|-3| is just the physical distance (left or right) of -3 from zero. Since we live in a physical world, all distances are positive, so its signed value is 3.
Since +3 is also 3 units from zero, |+3| = 3
|-3| = |+3| = 3 since both are three units away from zero.
So, when using absolute values as numbers, rather than distances,
|x| = x if x is not negative
|x| = -x if x is negative