Two co-planar lines, when drawn, are found in one graph of a Cartesian plane. We know that lines are made up of infinite points aligned in one direction only. So, when two non-parallel lines are graphed in one plane, they would eventually intersect. This intersection occurs in one point only. It will never intersect in more than one point unless it curves. But we know that this is not true with lines.
This is especially useful in a system of linear equations. When solving graphically, you can determine the solution of the system by looking at their point of intersection. The coordinates of this said point is the solution.
