Main differences between a List and a Set are...

Order : List collection is an ordered sequence of elements. A Set is just a distinct collection of elements that is unordered.

Positional Access : When we use a List, we can specify where exactly we want to insert an element. In a Set there is no order, so we can insert element anywhere without worrying about order.

Duplicate : In a List we can store duplicate elements. A Set can hold only unique elements.