parallel lines and transversal
We can clearly see three lines. Two are blue and one is gray. We can change the position of these three lines with free points A, B, C, D and E. We can see that the gray line (transversal) intersects the two straight parallel lines (blue) and makes interior angles b, d, e and h and exterior angles a, c, f and g. In this situation 4 types of angles are formed.
1. Corresponding angles
2. Alternate interior angles
3. Alternate exterior angles
4. Interior angles on the same side of the transversal
c and e, a and h, d and f and b and g are pairs of corresponding angles. d and h and b and e are alternate interior angles. c and g and a and f are alternate exterior angles. b and h and d and e are interior angles on the same side of the transversal. Move the free objects A, B, C, D and E and observe how the angles get changed.