Question 195439
These are lines that are either vertical (x=<someNumber>) or horizontal (y=<someNumber>)

For instance, a vertical line that passes thru the point (3,0) would be given by x=3

A horizontal line passing thru (1,5) would be given by y=5.

Lines in this form are really saying "I don't care what the value is for the other coordinate, but the  value of one coordinate is fixed at a specific number"