In mathematics, a plane is a Euclidean, two-dimensional surface that extends indefinitely. A plane is the two-dimensional analogue of a point, a line and three-dimensional space. Planes can arise as subspaces of some higher-dimensional space, as with one of a room’s walls, infinitely extended, or they may enjoy an independent existence in their own right, as in the setting of two-dimensional Euclidean geometry. Sometimes the word plane is used more generally to describe a two-dimensional surface

https://en.m.wikipedia.org/wiki/Plane_(geometry)