From Pyxis public wiki
A spheroid is a quadric surface in three dimensions obtained by rotating an ellipse about one of its principal axes. Three particular cases of a spheroid are:
- If the ellipse is rotated about its major axis, the surface is a prolate spheroid (similar to the shape of a rugby ball).
- If the ellipse is rotated about its minor axis, the surface is an oblate spheroid (similar to the shape of the planet Earth).
- If the generating ellipse is a circle, the surface is a sphere (completely symmetric).