1. it - Noun
2. it - Adjective
3. it - Pronoun
4. It - Proper noun
5. it - Determiner
The neuter pronoun of the third person, corresponding to the masculine pronoun he and the feminine she, and having the same plural (they, their or theirs, them).
As a substance for any noun of the neuter gender; as, here is the book, take it home.
As a demonstrative, especially at the beginning of a sentence, pointing to that which is about to be stated, named, or mentioned, or referring to that which apparent or well known; as, I saw it was John.
As an indefinite nominative for a impersonal verb; as, it snows; it rains.
As a substitute for such general terms as, the state of affairs, the condition of things, and the like; as, how is it with the sick man?
As an indefinite object after some intransitive verbs, or after a substantive used humorously as a verb; as, to foot it (i. e., to walk).
Source: Webster's dictionary