Corresponding angles are angles that are in the same position relative to lines intersected by a transversal.
In each illustration below, LINE 1 is a transversal of LINE 2 and LINE 3. In each illustration below, the following angles are corresponding angles:
When a transversal intersects two lines, the two lines are parallel if and only if corresponding angles are congruent (equal in measure).
In illustration one of the example section above, LINE 1 and LINE 2 are parallel and corresponding angles are congruent.
In illustration two of the example section above, LINE 1 and LINE 2 are NOT parallel and corresponding angles are NOT congruent.