What is the difference between perpendicular and parallel?

Perpendicular are intersecting lines that create a right angle, while parallel are two lines that are congruent in placement and will never intersect.

Parallel lines have the same slope and will never intersect. Parallel lines continue, literally, forever without touching (assuming that these lines are on the same plane). On the other hand, the slope ofperpendicular lines are the negative reciprocals of each other, and a pair of these lines intersects at 90 degrees.