What is the difference between absolute strength and relative strength?

Relative strength is the amount of strength to body size, or how strong you are for your size. Absolute strength is the maximum amount of force exerted, regardless of muscle or body size.

Well if you pick a machine to work on and that's gonna be your exercise if you don't stick to that machine your muscle strength your muscle mass rather will change because you haven't been doing it you change something in your exercise routine which changes your body's form of dealing with things for example you might become weaker or stronger depending on what kind of exercises you do in whether or not the machine you picked actually your muscles grow.