In Spanish, the endings of the conjugated verbs marks the person.
Sólo comemos vegetales y verduras. Somos vegetarianos. (Nosotros)*
Fui a llevar las cartas a la oficina de correos. (Yo)
Tienen muchas ganas de comer paella (Ellos/Ellas)*
That is the reason why it is not necessary to always put the subject pronoun, although there are three situations in which we cannot get rid off the subject pronoun.
Situations:
A.- When the first ("Yo") and third ("Él/Ella/Usted") singular person are the same. This always happens in the Imperfect and Conditional. We need the subject pronoun to know who we are talking about and avoid the confussion.
Examples:
Sólo comemos vegetales y verduras. Somos vegetarianos. (Nosotros)*
Fui a llevar las cartas a la oficina de correos. (Yo)
Tienen muchas ganas de comer paella (Ellos/Ellas)*
That is the reason why it is not necessary to always put the subject pronoun, although there are three situations in which we cannot get rid off the subject pronoun.
Situations:
A.- When the first ("Yo") and third ("Él/Ella/Usted") singular person are the same. This always happens in the Imperfect and Conditional. We need the subject pronoun to know who we are talking about and avoid the confussion.
Examples: