conversation：指非正式谈话，涉及一群或只有两个人 。
例句：None of them can carry out even the simplest conversation in the foreign language
they have been learning.
他们当中没有谁能用所学的外语进行即便（是）最简单的会话。
talk： 复数用的时候，意思是“或组织间正式的洽谈谈话”。
例句：We talked and laughed a lot. 我们畅怀说笑
talk with和conversation with的区别
talk with释义：
与…交谈
例句：
I had to have a heart-to-heart talk with her.
我得推心置腹地和她谈一谈。释义：
与…交谈
例句：
I had to have a heart-to-heart talk with her.
我得推心置腹地和她谈一谈。
conversation with释义：
与……谈话
例句：
Don was deep in conversation with the girl on his right.
唐与他右边的女孩在专心交谈。