all over the world 是全世界的意思。一般是副词词性,做状语。例如:we have friends all over the world。我们的朋友遍天下
而 among the world 一般是形容词词性,做定语。例如:
There is still massive food insecurity among the world’s poor, who often spend
more than half their income on food.
全世界贫困人口仍然面临着严重的食品不安全,他们一般在食品上花费超过一半的收入。