Basically they say their built-in technology allows them to block and identify zero-day malware without having the file on their database. Pretty much what heuristic on antimalwares do.
Actually, it's my understanding that the "heuristic analysis" in 1st gen AV products is basically a way of detecting new variants of known samples, by finding a common denominator -- either a recurring sequence of events or string of code shared by a family of viruses. It's a last-ditch effort to avoid imposing upon the user with alerts, by expanding the capabilities of signature-based detection as much as possible.
Problem is, this is still dependent on signatures. So all a malware coder has to do is alter the factor that the heuristics were relying upon, or write a whole, new virus. NGAV, on the other hand, is essentially HIPS with whitelisting. It's nothing new; the main difference is that the product uses a database of known legitimate applications and what they do, and/or scans the system upon installation to compile a database; and then blocks anything new. It's an acknowledgement of the fact that signature-based detection won't cut it anymore.