Given a equation of a line, you can graph the line. A system of equations is nothing but equations of more than one line. In a single equation all the points that lie on the line, satisfy the equation of the line. Similarly a solution of a system of equations is points that satisfy each and every equation of that system. A system of equations can have a single point as solution when the lines intersect at a common point, or have a unlimited points in solution when the lines overlap on each other or may not have a solution at all when the lines are parallel to each other. Graphing all the lines in a system of equations you can find the solution to it. This video shows how to solve linear system of equations by graphing them.