Fruit is usually used as a mass noun, and then it is used in its singular form. For example:
My doctor advises eating a lot of fruit.
I could make a fruit cake.
I bought some fruit at the market - bananas, oranges and apples.
However, the plural form ªfruitsª is sometimes used, in specific contexts. In that case, 'fruit' means 'the outcome of something, a successful result, or the part of a plant which develops from a flower'. You can use it also as a plural noun to denote different sorts of fruit. Hmmm, for example:
What are the fruits of our work?
The fruits of this land are ample.
Which fruits can you use in the production of brandy?