To understand the white list, it is best to understand the blacklist, a good understanding of the blacklist, the general meaning is that you reject the list, or you do not like the list, for example, we all use QQ, your friends into QQ blacklist, so He can not contact you That is to say you have rejected him or you do not like him, that means that a blacklist means a list you have rejected or a list you hate, presumably the meaning, and after understanding the blacklist, the white list is very Well understood, is the opposite of the blacklist.