What do parallel lines have in common regarding angles?

Parallel lines are defined as lines in the same plane that never intersect, meaning they maintain a constant distance apart. When considering angles formed by a transversal that intersects two parallel lines, one crucial property arises: alternate interior angles are always equal. This is a fundamental theorem in geometry related to transversal intersections, which states that if two parallel lines are cut by a transversal, the alternate interior angles formed on opposite sides of the transversal are congruent.

This property helps establish many other geometric relationships and proves useful in various proofs and problems. In contrast, while it is true that parallel lines do not intersect at any point, that statement does not specifically address angle properties, nor does it showcase the geometric relationship concerning angles created by a transversal. The other choices also reflect characteristics of parallel lines but do not highlight this particular angle property as clearly as the correct answer does.