1. Compare the following:
a. S/he was sitting between Bunna and Vitou.
I saw something lying between the wheels of the train.
Cambodia lies between Thailand, Vietnam and Lao.
b. We found a little house hidden among the trees.
S/he was standing laughing among a crowd of journalists.
We say that something is 'between' two or more objects, people, countries and so on when we see the surrounding objects and so on separately, there are not very many of them, and each one is clearly distinct from the others.
We say that something is 'among' a mass, a crowd, or a group: a collection of things when we do not see separately.
We prefer 'between' when we want to say that there are things, or groups of things, on two sides:
A little valley between high mountains.
2. Words like 'divide' and 'share' are followed by 'between' when we use several singular nouns.
He shared his property between his wife, his daughter and his sister.
I divide my time between teaching, writing and lecturing.
With plural nouns, 'between' and 'among' are both possible.
S/he divided his money between/among his five sons.
We always talk about the difference 'between' things.
What's the difference between a crow and a rook?
3. 'Among' can be used to mean 'one of', 'some of' or ' included in'.
Among the first to arrive was the Fantasian ambassador.
S/he has a number of criminals among his friends.