We can use it as an ‘empty’ subject or as an ‘empty’ object. It is ‘empty’ because it doesn’t refer to anything in particular:
I know it’s going to rain today!
It’s getting a bit late now, so let’s watch a DVD at home, shall we?
She doesn’t like it when you are so quiet.
How long will it be before he gives up smoking?
We also use it to introduce or ‘anticipate’ the subject or object of a sentence, especially when the subject or object of the sentence is a clause. Most commonly, such clauses are to + infinitive and that clauses. We also call this use of it a ‘dummy’ subject, since the real subject is another part of the sentence (real subject underlined):
It’s goodthat she’s doing more exercise. (or, more formally: That she’s doing more exercise is good.)
It was nice to talk with them again. (or, more formally: To talk with them again was nice.)
It’s quite likely that we shall be late, so please do start without us.
I find it amazing that …
With verbs such as find or consider, it + adjective + that clause or it + adjective + to infinitive, are commonly used to anticipate an object:
I find it amazing that they’ve never stopped arguing about football.
Not: I find amazing that they’ve …
I must say, local people will consider it to be an insult that they have not learned to speak a few words of the language.
I find itsurprising to see so many people here.
We also use it when a clause is the subject of a verb such as appear, seem, look, occur, which hedge or soften the statement, making it less direct:
It seems they’ve all lost contact since they met at the wedding.
It occurred to me that we might visit them while we are in South Africa.