The document discusses the difference between the words "preview" and "purview". It explains that "purview" is a noun that means "within the limits of what a person, an organization etc. is responsible for; dealt with by a document, law etc.". It provides examples to illustrate the usage of "purview". It also explains that "preview" can be both a noun and a verb. As a noun, it refers to an occasion where the press can see a film before public showing, and as a verb it means to see something before public showing and write about it. The document aims to strengthen understanding of English usage by highlighting how a single vowel change can impact a word's meaning.