Please help me when to use "fruit", when to use "fruits". Thanks

Oh, this is quite difficult. Quick answer:

Fruit (food):

There is a lot of fruit on the table.
There are different kinds of fruit on the table.

Fruits (non tangible, broadly meaning benefits):

These are the fruits of your labour.


I would guess that fruits can be used for the food version too, but I reckon it's as rare as using "peoples".