Final answer:
In geometry, a plane is a flat surface that extends infinitely in all directions.
Step-by-step explanation:
In geometry, another name for a plane is a flat surface. A plane is a two-dimensional object that extends infinitely in all directions. It has length and width, but no thickness.
For example, think of a sheet of paper. It is a flat surface that can be represented by a plane. Any figure drawn on the sheet of paper lies on the plane.
Similarly, in geometry, when we refer to a plane, we are referring to a flat surface that extends infinitely and on which figures and shapes can be represented.