1. What are subject pronouns?
The subject of a sentence is a person or thing that performs the action of the verb. Carlos is intelligent and Carlos is also handsome. (Carlos=Subject)
Subject pronouns are used to replace the subject (person or thing) of a verb.
Carlos is intelligent and he is also handsome. (he = subject pronoun)
Saying the word “Carlos" twice is repetitive and does not sound natural, so we replace the Subject (Carlos) that appears the second time with a subject pronoun to avoid repetition.

2. Subject Pronouns Yo = I Tú (informal) = You
Pronombres Personales
Yo = I
Tú (informal) = You
Él / Ella / Usted (formal) (Ud.) = He / she / you (formal)
Nosotros (as) = We (males or mixed) / We (females)
Vosotros (as) (only used in Spain) = You all (male or mixed) / You all (females)
Ellos (as) / ustedes = They (male or mixed)/ They (females)/you all

3. Points to keep in mind about Subject pronouns
Pronouns are the subject of a verb
In Spanish, subject pronouns can be singular or plural, and they can be masculine, feminine, or gender neutral.

4. Points to keep in mind about Subject pronouns
Spanish subject pronouns are both similar to and different from their English counterparts.
Let’s examine some of the differences.
- In Spanish there are two forms for –you- (tú, usted); - There are also two forms for -you all –
- There are masculine and feminine forms for -they- -you all- and –we-
-the subject pronoun –he- and –you (informal) have accent marks: él and tú.

5. recap “Usted” is more formal and is generally used to express respect.
“Tú” is more familiar and is used among friends, coworkers, relatives, or when addressing a child.
Speaking to your boss: usted Speaking to your daughter: tú Speaking to your teacher: usted Speaking to your friend: tú
This same distinction with regard to degree of formality occurs in the plural form as well. When referring to “you-all,” there are two choices in Spanish:
Ustedes = you-all formal
Vosotros = you-all familiar (only used in Spain).

6. Additional resources
Quiz: Video explanation:

7. The verb “ser” = to be I am Yo soy You are Tú eres
S.P (English)
Subject Pronouns + verb
I am
Yo soy
You are
Tú eres
He is / She is / You are
Él es / Ella es / Usted es
We are
Nosotros (as) somos
You all are
Vosotros (as / Spain) sois
They are
Ellos (as) son / Ustedes son