Many languages can drop the subject, or use one expression where English uses two. In English, a sentence always needs a subject (the word before the verb, like I, she, it), and there is and it is do different jobs.
1. Every sentence needs a subject
Even when the subject means nothing, English uses it: for the weather, the time, and before an adjective + to.
- It is raining. (not "Is raining")
- It is ten o'clock.
- It is important to sleep well. (not "Is important to sleep well")
2. There is / There are → something exists
Use there is or there are to say that something exists or is in a place, often when you mention it for the first time.
- There is a café near my office.
- There are three bedrooms in the flat.
- There is a problem with my phone. (not "It has a problem")
3. There is or there are?
- there is + one thing, or something you can't count (milk, water): There is a bus. There is some milk.
- there are + a plural noun: There are many people. (not "There is many people")
In questions and negatives: Is there...? Are there...? There isn't... There aren't...
4. There is first, then it
There is presents the thing. After that, it refers back to it.
- There is a new restaurant in town. It is very good.
- There is a problem. It is serious.
5. Common mistakes
- ❌ Is raining again.
- ✅ It is raining again.
- ❌ It has many people in the park.
- ✅ There are many people in the park.
- ❌ There is many reasons to stay.
- ✅ There are many reasons to stay.