Answer:
Parallel structure (also called parallelism) is the repetition of a chosen grammatical form within a sentence. By making each compared item or idea in your sentence follow the same grammatical pattern, you create a parallel construction.
Explanation:
Not Parallel:
Ellen likes hiking, the rodeo, and to take afternoon naps.
Parallel:
Ellen likes hiking, attending the rodeo, and taking afternoon naps.
OR
Ellen likes to hike, attend the rodeo, and take afternoon naps.