The document is a lesson on interjections, which are words used in sentences to convey emotion. It defines interjections as words that show emotion or sounds and are not grammatically related to the rest of the sentence. Common examples provided include "Wow!", "Yikes!", and "Ouch!". The document explains that interjections are usually followed by an exclamation point and can stand alone or be used within sentences. It encourages the strategic use of interjections in writing to demonstrate control over language and make compositions more engaging.