The Tesla page on it (https://www.tesla.com/autopilot) takes a while to get to describing what it does, but then says, among other things:
> Autopilot enables your car to steer, accelerate and brake automatically within its lane.
And:
> With the new Tesla Vision cameras, sensors and computing power, your Tesla will navigate tighter, more complex roads.
So it's steering... but you're supposed to leave your hands on the wheel anyway? But not actually steering, just resting there just in case? I'm not sure how realistic this is in terms of human behavior. To their credit, the page, at least as of this moment, also says:
> Current Autopilot features require active driver supervision and do not make the vehicle autonomous.
Reading just the web page, if you asked me "So, do you need to leave your hands on the wheel when autopilot is engaged on the freeway", I'd be unsure. Does "active driver supervision" mean "hands on the wheel"?
In general, it is very hard for humans to keep paying close attention to something they aren't involved in actually actively controlling, "just in case." I'm not sure if there's a way for this technology to be safe, if that's what it depends on to be safe. (not unique to Tesla).