The main vertical line going up the middle is generally refered to as the y axis, while the horizontal line that meets the yaxis in the middle is refered to as the x axis. the line that's going up...
The y-axis (not axle) is the set of all points on the coordinate plane for which x = 0. So if you are looking for the point on the line for which x = 0 then it must, by definition, be on the y-axis.