There is a difference. Generic nouns are used to talk about a class of thing, which can then be described in more detail or divided into other groups using other nouns. For example 'fruit', and then 'bananas, apples, oranges, etc'. Or 'tools' and then 'hammer, chisel, screwdriver, etc' A collective noun refers to a collection of things that form a group. For example 'a bunch of bananas', 'a herd of sheep', 'a flock of geese', etc.