这几个语句不懂意思，以及什么时候用

还有输入一串字符串，下面什么意思
scanf("%s"，a);
gets(a);什么时候用

他俩接受字符串的区别，请看:https://m.baidu.com/sf?pd=topone_trustpaper&resource_id=55858&word=C%E8%AF%AD%E8%A8%80%E4%B8%ADscanf()%E5%92%8C%E7%94%A8gets&ext=%7B%22url%22%3A%22https%3A%5C%2F%5C%2Fblog.51cto.com%5C%2Fu_15127571%5C%2F4040798%22%2C%22srcid%22%3A%2228420%22%2C%22jumptype%22%3A%22text%22%2C%22urlsign%22%3A%229795561207722339759%22%2C%22sitesign%22%3A%223168936243043761838%22%2C%22query%22%3A%22scanf%5Cu548cgets%5Cu63a5%5Cu6536%5Cu5b57%5Cu7b26%5Cu4e32%5Cu7684%5Cu533a%5Cu522b%22%2C%22token%22%3A%22ac3493%22%7D&top={%22sfhs%22:1}&atn=index&lid=11152000048632536771

有帮助的话采纳一下哦！