What would you call angles that are formed on opposite sides of a transversal and are between the two lines?

The angles formed on opposite sides of a transversal and located between the two lines are called alternate interior angles. This terminology arises from the arrangement of the lines and the transversal intersecting them.

When two parallel lines are intersected by a transversal, each pair of angles that appears on opposite sides of the transversal but inside the two lines are congruent. This congruence highlights their special relationship, and it is key in various geometric proofs and calculations, such as those involving parallel lines.

Understanding this concept is crucial because identifying the correct types of angles helps in reasoning through problems related to angle measures, especially in the context of parallel lines and transversals. The other options describe different relationships between angles, such as angles that are on the same side of the transversal or situated outside the two lines, which do not match the definition given in the question.