The word "either" is used to indicate a choice between two options. It helps to present alternatives, such as in the phrase "You can have either coffee or tea." In this case, the speaker is offering two distinct choices, and the listener must select one. In grammar, "either" can function as a conjunction or a pronoun. When used as a conjunction, it connects two clauses, while as a pronoun, it refers to one of two items. For example, "Either of the books is fine" suggests that the listener can choose one book from the two available options.