Also sometimes I see List used with new ArrayList? I typically always did ArrayList with new ArrayList
Is there a benefit of putting an ArrayList into a List vs an ArrayList?
List is the interface specified by the Collections API. ArrayList on the other hand is an implementation of this interface with special attributes (like fast random element access). LinkedList is another one (which can be faster for add and remove operations).
You usually pass around List objects to abstract away the implementation class, so you can replace the used implementation easily at a later point in time if another implementation seems to fit your use case better.
Most of the time this is however only needed when designing APIs, so passing around ArrayLists doesn't really hurt.