Like the title says, what does taking whey or any other protien accomplish when you are cutting?

Just wondering because I am interested in purchasing some protien but am unsure of what it actually accomplishes in cutting.

Protein = Muscle

It's the foundation of any diet. During a cutting phase, it allows you to hold onto LBM while shedding fat at the same time. Obviously it has to be coupled with good fats and carbs at appropriate times in order to reap any benefit.