What does this mean? |100|=

|x| is the absolute value function. It measures how far from zero x is, whether positive or negative.

|x| = x if x >= 0
That is, if x is not negative, |x| is just haw far away x is.

|x| = -x if x<0
So, if x is a negative value, |x| is still positive

Similarly, |x-10| is how far away from 10 x is.

So, |100| = 100
|-3| = 3