The document defines basic concepts about sets including: - Sets use curly brackets and do not repeat elements. Order does not matter. - The number of elements in a set is denoted by n(A). An element is in a set using the symbol ∈ and not in a set using the symbol ∉. - Operations on sets include union, intersection, subset, complement and empty set. - Venn diagrams can visually represent relationships between sets such as union, intersection, disjoint and universal sets. - The number of possible subsets of a set of size n is 2n.