Definition: In geometry, lines as we will as planes are two basic shapes. A line is a one-dimensional shape which has only length, no breadth or height. It may extend infinitely in both directions. On the other hand, a plane is said to be a flat surface that’s defined in two dimensions. It also extends infinitely far. The planes are commonly used in in two-dimensional Euclidean space. A number of fundamental concepts in geometry, graph theory, trigonometry, coordinate geometry are specified through the planes.