So here we have the following graphic representations of the solution set of a system of linear equations:
When both lines are the same one, that means that the system has infinitely many solutions. As you can see, there are infinite points where the lines intersect each other.
As you can see, both lines intersect exactly at one point, For this reason, this kind of system has only one solution.
As you can see, both lines will never intersect each other. For this reason, this system doesn't have a solution.