While引导的从句的谓语动作必须是延续性的，并强调主句和从句的动作同时发生（或者相对应）。并且while有时还可以表示对比。例如：
While my wife was reading the newspaper, I was watching TV. (was reading是延续性的动词，was reading和was watching同时发生) 。
I like playing football while you like playing basketball.
我喜欢踢足球，而你喜欢打篮球。（对比）
