Parallel lines are always the same distance apart: they never meet. On drawings, parallel lines are shown with arrows. If there is more than one pair of parallel lines on a drawing, then the arrows are doubled up for the second pair.
Perpendicular lines are shown with a square for the angle, rather than a curve.
On a graph, are the lines `x=0` and `x=1` parallel or perpendicular?
`x=0` and `x=1` never meet, so the lines are parallel.
A line CD is drawn at a right angle to the line AB. A second line is drawn at a right angle EF to the line AB. Are the lines CD and EF parallel?
Sketch the arrangement to see that the lines are parallel.