What was the Vevo thing on Youtube videos for?

Question

I don't notice it so much anymore, but I remember like ten years ago on YouTube almost every music video had the little Vevo stamp in the corner but was still available to watch on YouTube, so I never quite understood why it was there. What was Vevo? Was it a production company? A different streaming platform? I remember Adam Lambert doing a commercial/ad to promote Vevo, but never understood what it was or if it was another streaming platform separate from YouTube.