Q. 1. What does baptism by affusion mean?

A. 1. Affusion, from the Latin word affusio is the method of baptism where water is poured on the head of the person who is receiving the Sacrament. Affusio means "to pour on."

So "baptism by affusion" is the same as "baptism by pouring." That is the method of baptism presently used by the Catholic Church.