In discussions about autonomous driving, it’s easy to fall into a trap of defining the technology with a broad brushstroke. But there are explicit differences between something as simple as “semi-autonomous” (what we have on the road toady) and “autonomous” (what carmakers want on the road by next decade). This video from BMW helps explain the important distinctions.

In a nutshell, it dives into the five levels of autonomy—as defined by the Society of Automotive Engineers. (The top U.S. car regulator has a definition of its own, but it only goes up to Level Four, showing that BMW’s working off the SAE’s version.)

For the most part, what’s on the road right now can be defined as Level 2 (think Tesla’s Autopilot, for instance).

BMW has said it believes it’ll have a Level 5 vehicle ready to go by 2021. What’s that mean? My esteemed colleague Jason Torchinsky last year to explain:

As you can see, and as the video below conveys, Level 5 is full-on submission to robots.

There’s some debate over whether Level 3 autonomy should even be introduced—Ford being here—and Level 4 and Level 5 shouldn’t be expected until at least 2020. At Level 4, drivers in theory can turnover control of the vehicle to the car in nearly all situations, but, as BMV’s video explains, “they must, however, still be basically fit to drive in case they have to take over control of the car for specific sections of the journey.”

So if you want to brush up and fully understand how autonomous driving functions, take a look at the video below. It’s an extremely concise and helpful explanation of where things stand and where they’re headed.