continuous = "-ing" form of the verb = action in progress right now (often used for concurrent actions) He has drunk too much. (action completed) He has been drinking. (action may still be in progress or may continue shortly) I have been sitting here waiting for him to arrive. (my action of sitting is still in progress)

There are many grammar books which explain this and so it is not likely that we can do better! It would help if you could explain what you find difficult to understand and give us some example sentences you have seen to illustrate your difficulty. Then we can help you with more focus.