What kind of system do I have?????

We just built a new house and the plumber installed a water softener system. I asked what kind it was (this being our first water softener) and he wasn't sure. He had the water tested and installed the type he was given. I'm confused because there isn't a brine tank attached to this system. it's simply a round tank, about 5 feet high with a digital panel on the top. The plumber said we never have to do anything to it. Can someone help explain this system to me? I would post a picture, but I don't think I can on this forum. Any help would be greatly appreciated.