This second-person pronoun is used to directly address a person or a group of people. In many languages, including Spanish and French, there is a polite and informal form of you to be used in different contexts, however in English, this distinction does not exist.

At the turn of the seventeenth century, thee and thou reached an all-time high in written usage. However, by the 1620s, you had overtaken these now old-fashioned-sounding words.
In English there used to be both plural and singular forms of you. Thou (nominative) and thee (objective) were used to refer to an individual, while ye (nominative) and you (objective) were used to refer to a group of people or as a polite address. The nominative plural form ye gradually transitioned into you, making ye uncommon by the seventeenth century. The singular forms took on informal connotations, and fell out of usage in favor of the polite you. By the mid-1600s, you was used in the context that thee, thou, and ye had historically been favored.