An ellipse is a geometric shape that looks like a stretched circle. It is defined as the set of all points where the sum of the distances from two fixed points, called foci, is constant. This shape is commonly seen in the orbits of planets and satellites, where they follow elliptical paths around stars. Ellipses have two main axes: the major axis, which is the longest diameter, and the minor axis, which is the shortest. The distance between the foci determines how "stretched" the ellipse appears. In mathematics, ellipses are described by specific equations, making them important in fields like astronomy and engineering.