都能表示 吃 的意思,但还是有区别的,eat是只能是吃的意思,用法比如：eat sth,而have还有其他的意思
have to do sth 不得不作某事
have sb done sth 让某人作某事
have +名词：拥有某物,某物有的特征,接受、收到,进行,吃饭,等等
have back拿回
have had it 受够了
have it coming收到应得的报应
have it that说、主张
have off脱下,切断
have on 佩带
have something to do with与……有关
have got 拥有
这些是比较常用的词组,对于HAVE来说,用法实在太多,一下子是归不全的,have是一个很广义的词