This document discusses different types of cones in 3D geometry, including right circular cones and quadratic cones. It provides definitions and properties of cones, as well as theorems regarding their equations. Specifically, it states that the equation of a cone with vertex at the origin is homogeneous of degree 2, and that every homogeneous degree 2 equation represents a cone. It also defines a right circular cone as one generated by lines making a constant angle with the axis, and proves its cross-sections perpendicular to the axis are circles. Finally, it briefly mentions intersections of lines with cones and tangent planes/normals to cones.