An ellipse is a geometric shape that looks like a stretched circle. It is defined as the set of all points in a plane where the sum of the distances from two fixed points, called foci, is constant. The longest diameter of an ellipse is called the major axis, while the shortest diameter is known as the minor axis. Ellipses are commonly found in nature and various fields, including astronomy and physics. For example, the orbits of planets, such as Earth, around the Sun are elliptical in shape. This unique property of ellipses allows for interesting applications in engineering and design, such as in the construction of reflecting telescopes.