The answer to the first part is "absolute value"
The answer to the second part is "additive inverse"
The absolute value of a number is basically taking off the negative if one is present to begin with. For example, |-7| = 7 telling us that the location -7 is exactly seven units away from 0. If we were to add 7 to -7, then we get 0. Note how -7 is the additive inverse of 7. In a sense, the value -7 is the complete opposite of 7.