阿甘正传里有句：“mama always said an awful lot you can tell about a

阿甘正传里有句：“mama always said an awful lot you can tell about a person by there shoes”
an awful lot you can tell about a person by there shoes.意思大概说要想知道一个人的很多事情,只要看看他的鞋就可以知道.但是这个意思和语法上怎么分析呢?
为什么是you can tell about a person而不是you can know about a person