In this lesson, students use the coordinates on a coordinate grid to describe the location of rectangles. Students have used the grid, without coordinates, in other courses where they drew shapes and described their properties. In this lesson, students discover the usefulness of the numbers on a coordinate grid by trying to communicate to their partner the size and location of a rectangle. It gives students a reason to attend to the features of the grid and to use language precisely (MP6). Then students further exploit the coordinates using them to pick one rectangle out of a set of closely related rectangles all lying in different locations on the coordinate grid. Students are formally introduced to the terms coordinate grid, axes, horizontal axis, and vertical axis.