This document defines fundamental concepts about sets, including: - A set is a collection of distinct objects called elements. Capital letters denote sets and lowercase denote elements. - Sets can be finite, containing a countable number of elements, or infinite. The cardinality of a set refers to the number of elements it contains. - Basic set operations are defined, including union, intersection, complement, and subset/superset relationships. - Venn diagrams provide a visual representation of relationships between sets using overlapping regions. They illustrate concepts such as unions, intersections, and complements of sets.