Conic sections are shapes formed by the intersection of a plane and a double-napped cone. The four types of conic sections are circles, parabolas, ellipses, and hyperbolas. A circle is defined as the set of all points equidistant from a fixed center point in a plane. The standard equation of a circle is (x-h)2 + (y-k)2 = r2, where (h,k) represents the center and r is the radius. This document provides examples of writing and graphing circle equations in standard and general form.