The main kinds of pronouns are:

Subject: yo/I; tú, vosotros, usted, ustedes/you; él/he; ella/she; etc.
Demonstratives: esto, éste, ésta/this; ése, aquél, aquélla/that; etc.
Relatives: que, el cual/who; que, el que/that; etc.
Interrogatives: ¿qué?/what?; ¿cuál?/which?; etc.
Reflexives: yo mismo/myself; tú mismo/yourself; etc.
Possessives: mío, mía, míos, mías/mine; tuyo, suyo/yours; etc.

In Spanish, like English, subject pronouns are generally used only for emphasis of clarification.

cuadro26
SINGULAR		PLURAL
yo		nosotros(as)	we
tú	you (fam.)	vosotros(as)	you all (fam. pl.)
él	he	ellos	they (masc. or mixed group)
ella	she	ellas	they (fem.)
usted	you (form.)	ustedes	you all (form.)

The use of tú is reserved for those individuals whom you call on a first name basis. Usted is most frequently used with individuals with whom you've just met, or whom you refer to as mister or misses.

In Spanish it is not necessary to use the pronoun, since the end of the verb gives us the information that we needed to know the subject:

Cuando (yo) voy a la universidad, (yo) tomo un autobús./
When I go to the University, I take a bus.

(Nosotros) Queremos jugar al fútbol./ We want to play football.

The form ustedes is not very used actually. It's used vosotros.

There is no impersonal subject pronoun "it". The pronoun "it" is expressed by the third person singular verb form without subject.