The document discusses the Cartesian coordinate plane and functions. It defines the Cartesian plane as being formed by two perpendicular number lines called the x-axis and y-axis that intersect at the origin point (0,0). Each point on the plane is represented by an ordered pair (x,y) denoting its coordinates. A relation is a set of ordered pairs while a function is a relation where each x-value is mapped to only one y-value. The document provides examples of relations, tables, and mappings to illustrate these concepts.