**Definition:**
A conic section is a curve obtained by intersecting a cone with a plane. The main types of conic sections are circles, ellipses, parabolas, and hyperbolas.

**Key ideas:**
- **Circle:** A set of points equidistant from a center point.
- **Ellipse:** An elongated circle, formed when the plane cuts through both nappes of the cone.
- **Parabola:** A U-shaped curve that occurs when the plane is parallel to the cone's side.
- **Hyperbola:** Two separate curves formed when the plane cuts through both nappes at an angle.

**Why this topic matters in this category:**
Understanding conic sections is essential in mathematics as they have applications in physics, engineering, and computer graphics.