The document discusses tense and definiteness in English grammar. It defines tense as the linguistic indication of the time of an action, distinguishing between past, present, and future tense. Definiteness refers to whether a referent is known/familiar to the speaker (definite) or novel/unfamiliar (indefinite). The document provides examples to illustrate the uses and expressions of tense (e.g. walked, will go) and definiteness (e.g. the book, a book) in English.