What is ustedes in Spanish?
In Mexico, Guatemala, and Colombia "ustedes" is used for BOTH informal and formal -- it means "you all, you guys, y'all, etc."
¿Adónde van ustedes? = Where are you guys going?
Ustedes means talking to more than one person whom you respect. People you respect can be teachers, your parents, or elders. You wouldn't use "Ustedes" while talking to your friends. It is like "Ellos" and "Ellas" but you can also use it while talking to someone whom you respect. You can say: "¿Y ustedes?" or: "Ustedes tienen preguntas."
If you are form my father's generation (New York City) it means yous as in: Yous guys need to learn better English.
I suggest using the dictionary but ustedes (Uds.) is the plural of usted (Ud.), which is the singular & formal form of you. Ustedes (Uds.) is the plural & formal form of you. Also use Uds. in any other Spanish-speaking country besides Spain for any form of plural you (familiar or formal).