The document discusses inversion in English grammar. Inversion involves changing the typical subject-verb word order in certain contexts. It describes some common cases where inversion is used, such as for emphasis, in literary language, or with negative adverbs and conjunctions. Examples of different types of inversion are provided, including with complement-verb-subject word order and in sentences using negative adverbs like "never" or conjunctions like "not until". The document also provides exercises for learners to practice identifying and correcting examples of inversion.