Generally English requires verb phrases to have a subject. Without a subject, the clause would be ungrammatical.
I am learning English.
They are practising their speaking skills.
The car is going fast.
There are situations where we don’t use a subject. In the context of the clause, it is very common to use it.
Talking about weather
It’s cold (rather than: ‘The weather is cold’)
It’s hot
It’s raining (rather than: ‘there is rain outside’)
Talking about time
It’s late
It’s 3pm (rather than: ‘the time is 3pm’)
It’s time to go (rather than: the time is 9am which is the time we have to leave)
We also use it to avoid beginning a clause with a subject. We do this as it is easier to understand what is being said or written:
It is sometimes difficult to process information if the speaker or writer begins with the subject. (rather than: ‘Information is sometimes difficult to understand when the speaker or writer begins with the subject’)
It makes no sense to try changing it (rather than: ‘Trying to change it makes no sense’)
We use there to signify the existence of something:
There are strange noises coming from the forest
There might be a way to resolve the problem
There are very kind people.
There is used in the context of describing places:
There is mud on my shoes
Is there any food in the fridge?
There is a crack in the window
There is also used to signal to listeners or readers to pay extra attention to a point in a clause. There has the effect of delaying the information; it is used as the information or a subject that may be long or complex:
There is a population of over 200 million people in Brazil. (rather than just saying: ‘the population in Brazil is over 200 million’)
It is understood my most people that there are signs of global warming in every country. (rather than: ‘signs of global warming exist in every country’)
It is clear when reading the book that, there were are examples of animals becoming extinct because we cannot protect them. (rather than: ‘animals are becoming extinct).
In most cases, the dummy subject is more common. It also helps native speakers to prepare for the information that follows.
What examples can you think of?
What time is it now in your country?
How is the weather where you are?
What advice do you have for visitors to your country?