In three-dimensional space, two straight lines that appear to intersect can never intersect. In the mathematical definition, they are called parallel lines. The eyes can sometimes be deceiving, which is why our math is always a little bit worse. Parallel lines in three dimensions appear to intersect, but they are parallel. They can never either intersect or be perpendicular like those in a two-dimensional plane. The funny thing is that we live in a three-dimensional space and can never achieve the same simple relationship as in a two-dimensional plane.
Concept: the method of intersection of parallel lines