I've seen many facial moisturiser that is a "pore minimiser". what does that mean? and what is its benefit on the face?

Facial pores: Usually this means that the cosmetic is just actually masking the pores. It's like having 100 holes in the floor and covering them up with concrete that flows into the holes and covers them. There is nothing in terms of a cosmetic thing can actually make poor smaller, but we have various ways such as micro dermabrasion which can really help.