Mathematical point-sets, also known as LOCI, are collections of points in a two-dimensional space that can be used to describe a variety of mathematical concepts. They are often used to represent the solutions to equations or to graphically illustrate relationships between variables. LOCI can also be used to define regions in a plane, such as circles, ellipses, and other shapes. In addition, LOCI can be used to study the properties of lines, curves, and surfaces.