RecordList and the List Object

For each structure type RL<Type>RecordList is being created in java version, In the new outsystem9 we find a new class by name RL<Type>List  is also being created, Shall we know the significance of the new file. When an recordlist object is passed to an extension which type ( RL<Type>RecordList or RL<Type>List ) is passed ? Looks it passes either this or other based on the scenarios. Shall i know the significance which is passed when.