Usted and Ustedes are both forms of the English word "you." These two words are used in the Spanish language. One learning the Spanish language will have these words become among the first they learn. Both words are pronouns. Usted is a singular pronoun, while ustedes is a plural pronoun.
An example of the word usted in use is ¿Cómo se llama usted?. In the English language, this translates to What’s your name?. In the Spanish language, this is a sign of respect to get to know a person they just met. An example of ustedes being used is ¡Trabajen ustedes!, which means "You all work!"