This is the concept of systems of equations. This is where two lines are graphed and intersect in one spot, maybe they don't intersect, or maybe they are the exact same line.
If there is only one intersection, the only solution is that ordered pair. A no solution is when both lines are parallel to each other. All real numbers solution is when it is the exact same line for both equations.
The equation that is easiest to graph is the y-intercept form equation, (y=mx+b). This is actually the only way you can graph anything from and equation for a linear line.