Yeah, you'll sign a waiver before you go on the track, which will indemnify the track and its owners against any incident. And your standard road insurance will not cover you. So basically, you'll need to have some form of track-day insurance in order to cover yourself against any unforseen costs.
If some nutter drives into you, you could sue them for "uninsured losses", but this would only be worth pursuing if the loss was extreme. I would also recommend you checking your health insurance policy for similar exemptions.
