Yes, maybe they are just for ranking the activity of the users and might help in choosing the language partner. I've got many points and that's why I am wondering what can I do with them... Thank you Nanren888!

I think they are psychological. I suspect we are supposed to compete and feel achievement from the ever-increasing score, driven to make it rise higher next week. . Maybe it is a ranking system. Maybe as an aid to selecting langauage exchange partners? When I look at your profile, I see you have many points and must therefore be very knowledgable/useful. . Just guessing.