They started out separate but were bought by Google a couple of years ago. Prior to Google buying them, it was very helpful as you'd see delays much sooner than Google or other apps — though Google is not integrating the Waze reports into their system, so it is about as fast.
My big issue with Waze is some of the "bonehead" routing it does — there were several times where the route it wanted me to take was about as bad as waiting through traffic. For example, to get around a light, put me on a minor street and then have me turn left onto a 7 lane road with a 50 mph speed limit — very dangerous trying to make a left on that large a road with traffic at those speeds, and almost impossible to turn left because of traffic. Because of this, I quit using Waze a couple of years ago, for the most part, and I'm not sure if they've fixed some of those issues.