"Were" is the past tense form of the verb "to be." It is used to describe a state of being or existence in the past. For example, in the sentence "They were happy," "were" indicates that the happiness occurred at a previous time. It is commonly used with plural subjects, such as "they," "we," or "you." In addition to its use with plural subjects, "were" can also be used with the singular pronoun "you." For instance, "You were at the party" indicates that the action took place in the past. Understanding the use of "were" is essential for constructing accurate sentences in the past tense.