As you may know, the product owner originated from Scrum, where the role is responsible for “maximising the value of the product create.”  This sounds like a text-book product management responsibility to me. Nevertheless, the product owner is often regarded as a tactical role tasked with managing the product backlog, detailing requirements, and interacting with the development team. How come?
The confusion stems—at least partly—from the fact that Scrum is a simple framework focused on helping teams develop software. It does not cover common product management practices, such as, product strategy development, product roadmapping, and financial forecasting; and the only product management tool it offers is the product backlog.
Additionally, some approaches like SAFe employ a separate product manager and product owner role in order to facilitate scaling. Using a strategic product role and a tactical one is a common scaling technique. But calling the tactical role “product owner” is an unfortunate mistake in my mind: The SAFe product owner is not the same as the Scrum product owner! Having two different product owner roles adds to the confusion.
So why did Scrum introduce a product owner role at all? Why didn’t the framework use the term product manager? When Scrum was developed in the 1990ies, product management was different from what it is today. Product managers used to do the upfront market research, product planning, and requirements definition work. They would then hand off a requirements specification to a project manager who would work with development and test to deliver the product. The product manager would return only to issue change requests or help with the product launch.
This is in stark contrast to how things are done in an agile process, where product people are required to collaborate with the development teams on an ongoing basis—without neglecting the market and the internal stakeholders.
Secondly, Scrum is applied outside the realm of product development and commercial software products. Many organisations that have adopted Scrum like banks, retailers, and media companies traditionally don’t have a product management group and hence no product mangers. But they do have digital products that either help market and sell their revenue-generating offerings, such as, an online banking app, or they develop software that is used to automate business processes, increase productivity, and reduce cost.
By offering the product owner role, these organisations can start working in an agile way without the immediate need to establish a product management group and initiate an organisational change process. Instead, employees from the appropriate business units can—with some training and coaching—act as product owners . (In the long run, however, establishing a product management function is likely to be beneficial, as I discuss in my post “Five Tips for Introducing Product Management to Your Company.”)
So where does this leave us? My hope is that we will move past the divisive product manager-product owner debate and just talk about product people. 
In the short term, we should acknowledge that the product owner is a product management role. People playing the role should therefore acquire the relevant product management skills. As Marty Cagan and others, including myself, have pointed out, a two-day training course is not enough to become a competent product owner. Product management is a complex, multi-faceted discipline that takes time and effort to master.
Additionally, I recommend using either the term product manager or product owner in your company and qualifying it when necessary, for instance, by employing the terms senior and junior product manager / owner and strategic and tactical product manager / owner. This reduces confusion and helps unite people.
What matters are not job roles and titles. It’s the good we do for the users and our businesses.
 The quote is from the Scrum Guide 2016. Scrum was first used at Easel Corporation in 1993 to create a “design and analysis tool” according to Jeff Sutherland, see “Inventing and Reinventing SCRUM in Five Companies.”
The first Scrum product owner, Don Roedner, “had to own the vision for the product, the business plan and the revenue, the road map and the release plan, and (…) a carefully groomed and precisely prioritized product backlog for the team,” Agile Product Management with Scrum, pp. xv.
 Thanks to Rich Mirnov for introducing the term to me.