Skew lines are a type of non intersecting lines in space. You can identify skew lines when you look at the floor of your room as shown below.

Skew Lines Introduction

The edges formed by the walls with the floor form skew lines with the intersecting lines of the walls as shown in diagram. The skew lines are shown shaded with same colors.

Let us now look how the skew lines are different from parallel lines (the type of non intersecting lines you are already familiar with).

Non coplanar lines in space that do not intersect are called skew lines. Segments and rays contained in skew lines are also skew. Let us identify the skew edges of the cube ABCDEFGH.

Skew Lines Definition

1. Edges AB and CD.                      2. Edges AB and GH.
3. Edges BC and AF.                       3. Edges BC and GH.
5. Edges CH and AF.                       6. Edges CH and BE.
7. Edges AH and BE.                       8. Edges AH and CD.
9. Edges DE and AF.                       10. Edges DE and GH.
11. Edges EF and GH.                    12. Edged EF and CD.
13. Edges FG and BE                     14. Edges FG and CD.
15. Edges GD and BE.                    16. Edges GD and AF.

You may also note any diagonal of a face is skew to the edges of the opposite face, like AC is skew to GD.
The angle between two lines the angle between two coplanar lines drawn parallel to the two lines.