The word "food" is usually uncountable. Like water or air, "food" is generally a mass noun that cannot be counted. For example, "The refugees need food, clothes, and medicine".
But, like many mass nouns, "food" can be used as a countable noun to mean "types of...". So just as you can say "We sell many different teas" ( meaning kinds of tea), you can say "foods" to mean "different types of food". For example, an international food fair would sell "foods from around the world".