The document discusses two-dimensional loci and their construction. It defines locus as the path of a moving point or set of points satisfying given conditions. Examples of loci include circles, lines, ellipses, and arcs. The key types of loci are those where a point is a constant distance from a fixed point or line, equidistant between two fixed points, and bisecting the angle between two intersecting lines. Intersection of two loci occurs at points satisfying the conditions of both loci.