As you can notice, in Italian there are two ways of saying "you" in the singular: formally and informally.
In Italian, we use Lei (sometimes capitalized) for formal situations (strangers, superiors, or elders) instead of the informal tu. Although lei literally means "she," as a formal "you" it applies to both men and women.
Grammatically, it uses the third-person singular verb form (the same as he/she). So, "You are" becomes Lei è.
Importantly, while the pronoun is feminine, adjectives must still match the actual gender of the person being addressed. E.g. For a man, you say Lei è stanco; for a woman, Lei è stanca.