Alternate Exterior Angles
When two lines are crossed by another line (called the Transversal):
Alternate exterior angles are a pair of angles on the outer side of each of those two lines but on opposite sides of the transversal.
In this example a and h are a pair of alternate exterior angles
Also b and g are a pair of alternate exterior angles.
To help you remember: the angle pairs are on alternate sides of the transversal, and on the exterior of the two crossed lines.
Note that alternate exterior angles are outside the two lines. When the angles are between the two lines, they are Alternate Interior Angles
Parallel Lines
When the two lines being crossed are Parallel Lines the alternate exterior angles are equal.
images/parallel-pair.js
(Click on "Alternate Exterior Angles" to have them highlighted for you.)
2111,2112