Known for its egg-like sulphur smell, NAC is the precursor to Glutathione similar to the way a pro-drug metabolizes into another drug, this powerful supplement gives the body the ingredients to make intracellular Glutathione. 
Here are a few reasons to take NAC (N-Acetyl Cysteine). The science supports the positive benefits of this powerful antioxidant and its role in fighting cancers.
I won’t claim to know everything about NAC (aka N-Acetyl-Cysteine) and it may sound a little like “bro science” but I have culled from my readings that it is a very effective detox supplement. It is a precursor to Glutathione, helps with methylation (I’m paraphrasing from memory) and if you wanted to get this naturally through diet you should eat brussels, broccoli, cauliflower and other cruciferous vegetables, of which broccoli sprouts are said to be superior according to Rhonda Patrick on Joe Rogan podcast. Sulforaphane is another closely related topic here, and here is a paper about bioavailability. It is also probably the reason this supplements smells sulphurous or like rotten eggs.
From the side of its bottle: “N-Acetyl Cysteine (NAC) is a stable form of the non-essential amino acid L-Cysteine. It is a sulfur-containing amino acid that acts as a stabilizer for the formation of protein structures, and is alos necessar for the formation of Glutathione which exerts a variety of protective effects, including detoxification and intracellular defense against oxidative stress.”
And here is another scientific paper about this very powerful antioxidant, anticancer supplement.