Firstly, they are grammatically different. 'Food' is nearly always uncountable (food/some food), whereas 'dish' is countable (a dish, some dishes). Food is a general word to refer to fuel for the body. People eat food, animals eat food. You can even give food to a plant to help it grow better. A dish is a set of ingredients combined and prepared together to make a particular speciality. For example, 'kofta' is a famous Turkish dish. You might say 'The food in that restaurant is very good. You can get a lot of lovely Turkish dishes there'. I hope that's all clear.

Dish refers to a plate of prepared food. You can't always use dish to talk about a specific food, for example, sweet potatoes. It has to be prepared and plated. Basically, any food that is prepared and served is referred to as a dish. The word food is a general term that applies to any form of nourishment.

dish for use and food for.eat

Dish means some particular food. And food means any dish.