Observaciones

(In the following list of observations, all subject pronouns are in bold.) 

• Tú is a familiar pronoun used for people you address by their first name or whom you know well.   
• Usted (Ud.) is a formal pronoun used for people you address by title, by last name, a figure with authority, or whom you don't know well. 
• Vosotros and vosotras is a familiar plural pronoun used only in Spain for people you address by first name.
• Ustedes (Uds.) is a formal plural pronoun in Spain. In other Spanish speaking countries, it is formal or informal and designates only the plural. 
• Nosotros, vosotros, and ellos are used when referring to all male groups or groups that have at least one male person. 
• Nosotras, vosotras, and ellas are used when referring to all female groups. 

Gender in Spanish

As with all romance languages, Spanish nouns show grammatical gender: la mesa, el árbol (the table, the tree). Articles, adjectives, and pronouns match the grammatical gender of the noun they describe. At the time of this writing in summer 2022, Spanish has not yet developed a consistent gender-neutral pronoun or gender-neutral adjective ending. Several have been proposed: the arroba @ - (for example, chic@), an X (as you may have seen in the descriptor Latinx, widely used in the United States), and the pronoun elle (which takes adjective endings of -e). 

For more information, see Wikipedia's entry on Elle.