感觉百度百科讲的比较清楚
https://baike.baidu.com/item/%E7%99%BD%E5%99%AA%E5%A3%B0%E5%BA%8F%E5%88%97/8436886?fr=aladdin
下面的链接里讲的比较粗糙，但是也很清楚
https://blog.csdn.net/qq_16050561/article/details/87719547?utm_medium=distribute.pc_aggpage_search_result.none-task-blog-2~all~baidu_landing_v2~default-1-87719547.nonecase&utm_term=%E9%9D%9E%E7%99%BD%E5%99%AA%E5%A3%B0%E5%BA%8F%E5%88%97%E6%98%AF%E5%B9%B3%E7%A8%B3