In algebra, you've already used the coordinate plane for plotting points, so you're familiar with at least one example of a plane. Also, remember that the surface of a plane has no thickness. At least three points not on the same line are needed to define a plane. Finally, there is space, the set of all points. You can think of it as an open, empty room, or the inside of an empty box.
Space has no boundaries and extends endlessly in all directions.
Of course, these four terms are just the beginning. You'll encounter many more words and their meanings as you work through this geometry course. Before you move on, here are three more basic terms to become familiar with. You'll be seeing them often. Line segment A line segment is simply a part of a line that has a specific length and specific endpoints.