That is a difficult question because so many answers are possible depending mostly on the context and previous knowledge of the person asking. A very quick basic attempt at an answer: integers are good for things that you mostly get in wholes and can count. Floating point is for numbers that can be anything, including anything in between two adjacent numbers.
Bulk product (like sand) is typically measured in tons and you can get 2.5 tons. That would require a floating point number.
Apples, oranges, packages, number of cookies in a box, number of bottles in a crate, number of identical bags/boxes on a pallet, products that are made one by one are typical integers. Up to the point where you get so many of them that you trade tons instead. Then you would prefer floating point again.