Tu and usted are two different ways to say you in Spanish. Tu is the informal way of saying you. A speaker would use it when talking to friends or someone they know well. The textbook states that it could also be used when talking to a family member or a child. Usted is the formal way to say you. A speaker would use it when addressing someone to show respect. When talking to someone you do not know, a teacher, or an older person usted should be used. Ustedes is plural. It is used when two or more people are being addressed. Unlike tu and usted, ustedes can be formal or informal.
