Answer:
When just two people are involved, we often use "between", whereas "among" is used when more than two people are involved.
However, the above answer seems to be not fully correct.
www.wikidifference.com/difference-between-among-and-between-2/ It is not wrong to use among for between. But it will be wrong to use between for among.
www.wikidifference.com/difference-between-among-and-between/ This has a detailed description.