Do you need to know anything about Vietnam?

khanh44 wrote:

ah I think I get.

Chung ta refers to 2 person and chung toi refers to 2 or more people? Is that how it works?

No, it's not like that. Both "Chung ta" and "chung toi" are used to refer to from 2 persons or more. See:

1. I'm talking to you and I want to go to coffee shop with you, I may say: "Chúng ta đi uống cà phê nhé?" means " How about if we go to the coffee shop now?". In this case: Chúng ta = we = you and I.

2. I'm taking to you and your fiance and I want all of us go to the  coffee shop, I may say: "Chúng ta đi uống cà phê nhé?". In this case: Chúng ta = You and I and your fiance.

3. I'm telling you about what I did during the Tet holidays of last year. I did lots of thing with my family and all of us were happy. I can say: "Chúng tôi đã rất vui" means "We all were happy". In this case: Chúng tôi = we= I and other members of my family.

4. You and I and your fiance are sitting in a coffee shop. Then you and your fiance have to go for somethings, so you can say: "Chúng tôi phải đi rồi,bla bla...." means "We have to go now,bla bla ....". In this case: Chúng tôi= You and your fiance.

Hope that all above can help you understand when you should use "Chúng ta" and when you should use "Chúng tôi"