Use tú when you are talking directly to a child, a relative, a friend, a peer, or a pet, you should use tú, the informal second person singular.
Vos is used instead of tú in some countries, such as Argentina, Paraguay, Uruguay, Nicaragua, and Costa Rica.
In some countries, such as Bolivia, Chile, Honduras, Guatemala, and El Salvador, you may hear both tú and vos.
In some countries, such as Spain, Mexico, Puerto Rico, Cuba, and the Dominican Republic, you will only hear tú.
Usted is used to directly address someone older, a person you do not know, a superior, or someone to whom you would like to show respect.
Use nosotros or nosotras when speaking about a group of which you are a part.
The difference between nosotros and nosotras is gender.
- Nosotros is used to refer to a group of men only or a group made up of men and women. Even if there are ninety-nine women and only one man in a group, you still use nosotros.
- Nosotras is feminine and is only used when the entire group is female.
Vosotros and vosotras are used to speak directly to a group of people you are very familiar with.
Vosotros and vosotras follow the same rules for gender as nosotros and nosotras.
In Latin America, ustedes is used to speak directly to a group of people in both formal and informalsituations.
In Spain, ustedes is used when talking to a group of people in a formal situation.