1.when指某个时间点,表示瞬间动作；while 指某个时间段,表示延续性动作.如：
When I got there,she was playing the violin.我到那里时,她正在拉小提琴.
While I was playing the violin,he came to see me.我正在拉小提琴时,他来看我了.
补给站：英语中,延续性动作是由延续性动词发出的,瞬间性动作是由非延续性动词发出的.延续性动词和非延续性动词的区别：
延续性动词是指该动作可以延续一段时间,而不是瞬间结束,如work（工作）、study（学习）、eat（吃）、watch（观看）；非延续性动词是指该动作极为短暂,瞬间便会结束,如start（开始）、begin（开始）、hit（撞）、see（看见）、knock（敲）、jump（跳）.
2.when表示偏偏在这时,强调双方动作互相冲突；while表示与此同时,双方动作互不相干.如：
When we were having a meeting,the children were shouting outside the window.我们正在开会,孩子们却在窗外大喊大叫.
While we were having a meeting,the children were watching TV in the next room.我们开会时,孩子们在隔壁房间看电视.
3.when排斥一般时间概念,泛指某特定情况；while表示趁有条件时,强调抓紧时机.如：
When in Rome,do as the Romans do.
入乡随俗.
While in Rome,he visited some of his old friends.他在罗马的时候,拜访了一些朋友.
4.用于完成时,when表示“在……之后”,while表示“在……期间”.如：
When he had joined the army,he was sent to the front.他服役后,被派往前线.
While he has been in the army,he has done lots of good deeds.他服役期间,做了许多好事.