Theory:

Alternate interior angles:
Interior angle.png
 
The region between the two lines \(m\) and \(n\) are known as interior regions and the located in this region called interior angles.
 
Now observe the above diagram, there each of pair of angles named \(∠a\) and \(∠b\), \(∠c\) and \(∠d\) are marked on the opposite side of the transversal line \(l\) and are lying between lines \(m\) and \(n\) are called alternate interior angles.
The each pair of alternate interior angles are equal, only when a transversal cuts the two parallel lines.
Alternate Exterior angles:
Screenshot 2020-10-14 152403.png
 
In the above diagram, we can notice each pair of angles named \(∠1\) and \(∠7\), \(∠2\) and \(∠8\) are marked on the opposite side of the transversal line \(l\) and are lying outside of the lines \(m\) and \(n\) are called alternate exterior angles.
The each pair of alternate exterior angles are equal, only when a transversal cuts the two parallel lines.