Predicate logic, also known as predicate calculus, is the branch of logic concerned with modeling statements like All men are mortal
that propositional logic is incapable of doing. It is built around two cornerstone ideas: predicates and quantifiers.
Typically, when one learns propositional logic, it's almost a no-guess to learn predicate logic as well. This is because it's closely related to the former and, honestly, quite easy to pick up. In computer science, must of the logical reasoning applied has strong roots in predicate logic.