Hola Eya

Usted is a pronoun used formally for a "you singular", for example when you are talking to elderly people or in general for more formal situations like when you are in a bank or in a job interview, etc. 

Vosotros is also a pronoun used only in Spain (not Latin America) for a "you plural" - it's the generic informal pronoun in Spain, so you'd use it to refer to more than one person. If the situation is more formal then you use the more formal pronoun "ustedes". 

Note that in Latin America the "ustedes" pronoun is always used, for informal and formal. 

I hope this clarified it. 

You can also have a look at some lessons and informative articles where we mention usted, ustedes and vosotros:

tú vs usted

formality 

español peninsular

español latinoamericano

Saludos cordiales

Inma