This is a very good question. People in Brazil sometimes make the same mistakes when speaking English because of a small but sill important difference in the use of these verbs. So, let's go: The verb HAVER means THERE IS/THERE ARE. Example: Há uma pessoa batendo na porta - There is someone knocking on the door. No change in plural: Há duas pontes sobre este rio - There are two bridges over this river. The verb TER is the one that causes all of this confusion. It means HAVE, bul also THERE IS/THERE ARE. And how do you know when it means each of its meanings? In fact it is easy. When it means THERE IS/THERE ARE, it is impersonal (there is no subject in the sentence). Example: Tem uma pessoa batendo na porta (There is someone knocking on the door) - or, in the plural, Tem duas pontes sobre este rio (There are two bridges over this river). In both sentences there is NO SUBJECT in the sentence. Now compare them: Tem alguém batendo na porta = Há alguém batendo na porta (no subject in either: "Haver" is impersonal and "ter" with the meaning of "haver" is also impersonal). Now see the verb TER meaning TO HAVE. In this case, it is NOT impersonal. It does have a subject. For example: Eu tenho um carro (I have a car). Ele tem um ingresso para o show (HE has a ticket for the concert). You got that? Now, the mistake people sometimes make in Portuguese is to say things like "In my city has a soccer stadium." They should say In my city THERE IS a soccer stadium, but they think of the verb TER as meaning THERE IS, and translate it to its most known meaning, TO HAVE. I hope it was clear. Cheers from Brazil By the way, HAVER is more formal. TER with the meaning of THERE IS/THERE ARE/EXIST is kind of substandard.

It would be better to see a dictionary.. But in general, It is like: For possession we only use "ter", like "Tom has a car" -> Tom tem um carro. For position, existence.. we can use both: There is a person on the street -> Há uma pessoa na rua/Tem uma pessoa na rua Using "TER" in this case is considered less formal. It would be better for you to consult the "formas compostas do verbos" in order to get a wide view of the other uses of it, because in theses cases they tend to be interchangeable, though "haver" is slightingly more formal.