From Teflpedia

An audiobook consists of an audio recording of a narrator (e.g. actor) reading a book. Some people prefer them over print books, sometimes out of necessity (e.g. due to visual impairment), sometimes they are more practical than books (e.g. while driving).

Graded readers for English language learners often come with accompanying audio tracks, intended to practise listening, particularly extensive listening. If used together with the written text this becomes reading while listening.

They can also be sped up/slowed down to taste.