be with sb和together

be with sb和togetheri want to stay with you和i want to stay with you together两句的意思有什么区别be with sb不就是和某人在一起的意思吗,那干吗还加together那么说“今天我和Sam一起吃的午饭”除了sam and i had lunch togerther today,还能说成i had lunch with sam today吗?我只有7分了.不好意思