Suppose you are measuring altitude. You measure a hill, and it's 350 m tall. You measure another hill, and it's 150 m tall. You come to a valley. It's 75 m below your point of reference: you mark it down as being -75 m in altitude. If you jumped off the first hill to your reference point, you'd fall 350 m, the absolute value of the measurement. If you jumped from the reference point into the valley, you'd fall 75 m, the absolute value of the measurement.

You can think of absolute value as "distance from zero":

5 is 5 units away from zero.

-5 is also 5 units away from zero.