1- Asychronous(异步)
If x does y asynchronously, then x does not wait for y to complete before doing next thing.
如果x任务异步执行y任务,就相当于x任务还没等y任务完成,就去做
下一个任务。
2 - Sychronous(同步)
If x does y sychronously, then x waits for y to complete before doing next thing.
如果x任务同步执行y任务,就相当于x任务等待y任务完成,才执行下一个任务。