Verbs 101: the concept of persons
In order to understand how verbs (action words) work one must comprehend the concept of persons. Each verb can be broken down into three singular persons and three plural persons, for a total of six. By persons, I mean the person who is performing the action.

Singular persons:
1st person singular: Translates as "I" and is the person doing the talking.
2nd person singular: Translates as "you" and is the person to whom you are speaking.
3rd person singular: Translates as "he, she, it" and is the person you are talking about.

The Spanish equivalents are as follows:

1st person singular: "I" in English translates as YO
2nd person singular: "You" in English translates two ways, both TU and USTED.
3rd person singular: "He" in Spanish translates as él" and she as ELLA. Spanish does not have a subject pronoun for the word IT. "IT" is assumed in the verb, such as "es lunes" meaning [It] is Monday.

Plural persons:

1st person plural: Translates as "we" and are the persons doing the talking.
2nd person plural: Translates as "you all " and are the persons to whom you are speaking.
3rd person plural: Translates as "they" and are the persons you are talking about.

The Spanish equivalents are as follows:

1st person plural: "We" in English translates as NOSOTROS or NOSOTRAS (9if all members of the group are feminine)
2nd person plural: "You all" in English translates two ways, both VOSOTROS (only in Spain) and USTEDES.
3rd person singular: "THEY" translates as ELLOS (all male or mixed gender group) and ELLAS (all female group).

In the practice exercise, select the correct Spanish subject pronoun.