what does it called when you help someone, then you ask him that he should help someone else to keep it going?

Question

let's say that i asked someone for an assist in something, she did helped, and when i asked her, she say: i help you out, you help someone else out, and so on and so on...
So, is that called Karma, or it called something else, i think i did read or hear ppl name it with something that i can't remember what was the name? any one knows???

Answer 1

Chain.

Answer 2

It is called Pay It Forward.

Answer 3

it is a movie called " Pay It Forward"