Examples of Skew Lines

'Skew lines' is a very broad definition of lines which are 'not parallel, but do not intersect'. They're also not therefore on the same plane. This is a very relevant part of 3D geometry, dealing with the interaction of lines between points in a three dimensional structure. Skew lines are 'normal' lines in these structures, unless one point of their ends is co-planar with another. They can also be used as correlatives when designing structures, because of this requirement for non-co-planar alignments. In architecture, for example, some lines are supposed to be non-co-planar, because they're part of a three dimensional structure.

Examples of Skew Lines:

https://en.wikipedia.org/wiki/Skew_lines
https://simple.wikipedia.org/wiki/Skew_lines

Image Example of Skew Lines:

A fibration of projective space by skew lines on nested hyperboloids.