Typical structures are as follows:
Something exists – There are many possibilities.
Something happens – There’s a football match every Sunday.
Number or amount – There are twelve students in this class.
With modals – There could be a problem.
We can use it to introduce new information. Typical structures are as follows:
Times, days, dates – It’s one o’ clock. It’s Tuesday.
The weather – It’s raining. It rained all night.
Opinions – It was a difficult choice.
Adjectives – It’s strange (that) we’ve never spoken before.
With expressions like:
It looks like…– It looks like it’s going to rain.
It seems/appears…. – It seems/appears that our new teacher is a man.
It refers back to something already mentioned:
There is a shop at the end of this street. It is open every day.
There can refer to a place:
A famous writer used to live there.