The equation x = 5 represents a vertical line. This line consists of all points where the x-coordinate is always 5, regardless of the y-coordinate. Therefore, no matter what value you choose for y, the point will be on the line as long as x is 5.
To visualize this, you can imagine plotting points such as (5, 1), (5, 0), and (5, -3) on a coordinate plane. All these points lie on a straight line that runs up and down, crossing the x-axis at the point x = 5. In contrast, horizontal lines are represented by equations of the form y = c, where c is a constant. Thus, the line described by x = 5 is definitely a vertical line.