Product owner teams are a way to keep your backlogs well groomed and ready to work on. In many companies the concept of “Single Wringable Neck” does not really work.
Large products have many different feature lines or initiatives each of which may have one or more product owners. Clearly there is more work and a lot of time that needs to be invested in keeping the product backlog for your product.
A product owner teams is a scrum team with many product owners often with some developers and testers that meet many times a week to talk about a product backlog , meet customers. Think of this team as a group of fitness instructors in a gym who also need to work out in order to keep you in goods shape.
This document outlines more details about how to set up product owner teams