区别是：
eat 流行于美国,既可指“吃”,也可指“喝”,但作“喝”讲时通常用于“喝”汤之类。
have为普通用语，有吃喝的意思，在英国常用have代替drink，在美国常用eat代替have，与meal,dinner等表示三餐的词连用时多用have，而不用其他词。
例句辨析：
eat
1、She was eating a sandwich.
她在吃三明治。
2、Let's go out to eat.
我们出去吃吧。
3、The bananas should be eaten within two days.
那些香蕉应该在两天内吃掉。
have
1、She had agreed to have dinner with him in town the following weekend.
她答应下一个周末和他在城里共进晚餐。
2、Phone him up and tell him to come and have dinner with you one night.
给他打电话，告诉他哪天晚上过来和你一起吃饭。
3、How would you like to have dinner one night?
哪天晚上和我一起吃饭好吗？
