That is a slightly complicated question. In general, use 'fruit' for the food, and use 'fruits' in a biological context.
If you want to explicitly refer to several types of fruit, e.g. at a fruit shop, then use 'types of fruit', or 'kinds of fruit'.
I like fruit with my breakfast. That shop sells fruit and vegetables. There are four different types of fruit in the bowl.
The fruits of several trees in this area are edible.