In short we can say that, exterior angles that lie on the same side of the transversal are called consecutive exterior angles, and those that lie on opposite sides of the transversal are called alternate exterior angles.
http://www.mathcaptain.com/geometry/consecutive-exterior-angles.html
Converse also true: If a transversal intersects two lines and the interior angles on the same side of the transversal are supplementary, then the lines are parallel. The sum of the degree measures of the same-side interior angles is 180°.
https://www.wyzant.com/resources/lessons/math/geometry/lines_and_angles/angle_theorems
If a transversal intersects two parallel lines, the pairs of corresponding angles are congruent. Converse also true: If a transversal intersects two lines and the corresponding angles are congruent, then the lines are parallel. The figure above yields four pairs of corresponding angles.
https://www.wyzant.com/resources/lessons/math/geometry/lines_and_angles/angle_theorems
While some postulates and theorems have been introduced in the previous sections, others are new to our study of geometry. We will apply these properties, postulates, and theorems to help drive our mathematical proofs in a very logical, reason-based way.
https://www.wyzant.com/resources/lessons/math/geometry/lines_and_angles/angle_theorems
Definition of Base Angle Theorem. Base Angle Theorem states that if two sides in a triangle are congruent, then the angles opposite to these sides are also congruent. 1  Base angles of an isosceles triangle are equal.
http://www.icoachmath.com/math_dictionary/base_angle_theorem.html
1 Base angles of an isosceles triangle are equal. 2  Converse of the base angle theorem is also true, i.e. if two angles of a triangle are congruent, the sides opposite to these angles are congruent.
http://www.icoachmath.com/math_dictionary/base_angle_theorem.html
Consecutive exterior angles are formed when two lines are intersected by a transverse line in a same plane. A transverse is a line that intersects two or more lines in the plane at different points.
http://www.mathcaptain.com/geometry/consecutive-exterior-angles.html
Converse also true: If a transversal intersects two lines and the alternate exterior angles are congruent, then the lines are parallel. The alternate exterior angles have the same degree measures because the lines are parallel to each other.
https://www.wyzant.com/resources/lessons/math/geometry/lines_and_angles/angle_theorems
Alternate Exterior Angles. more ... When two lines are crossed by another line (which is called the Transversal), the pairs of angles: • on opposite sides of the transversal • but outside the two lines are called Alternate Exterior Angles. When the two lines are parallel Alternate Exterior Angles are equal.
https://www.mathsisfun.com/definitions/alternate-exterior-angles.html
1 Converse of the base angle theorem is also true, i.e. if two angles of a triangle are congruent, the sides opposite to these angles are congruent.
http://www.icoachmath.com/math_dictionary/base_angle_theorem.html
definition of exterior angles theorem
The exterior angles theorem is defined when two lines are intersected by a transverse line in a same plane.