你说的是表示“...时”的区别吗?
when和while都能表示这个意思,但是while后面必须用进行时态.
另外,while可以表示“而”表示对比,这时,while后面不一定要用进行时
如：
He came back when I was watching TV.对
He came back while I was watching TV.对
He came back when I went to work.对
He came back while I went to work.错
表示对比关系时：
He went to bed while I went to work.
He was sleeping while I was working.
换成when也说得过去,但你的老师会算你错,因为他考的就是你的辨别能力.
另外,用while时,其两边的句子结构要对称.