The Seattle area is notorious for blending job titles and functions when it comes to the product managers and product marketers. In fact the majority of people I talk to think they are one and the same. In my opinion, they are very different, especially for a company that is truly customer centric.
Product Management = Inbound
Fundamentally, true product managers have a very important job; they are tasked with representing to the company the needs, pains and opportunities in the market.
They conduct research, watch the market, use related products, read between the lines, ask questions, do competitive analysis, ultimately using their "voodoo powers" to assess and size a given market/business opportunity.
If they do their job, not only will their company be able to depend on them to be the ultimate customer advocate at both a tactical and strategic level, but the product's capabilities and long term roadmap will set the company up for great success.
Product Marketing = Outbound
Product marketers represent to the market the products & services a company offers. They deal in the art of mapping the product's current (and future) capabilities into value propositions that resonate in the marketplace.
They handle analyst engagement, positioning, branding, PR, marketing communications, campaigns, lead generation, etc.
If they do their job, the product they bring to market will successfully resonate with current and prospective customers, ultimately propelling their sales against the competition.
Over the last 10 years, I have had the pleasure of working with rock star product people and rock star marketing people. I have yet to find anyone who is a rock star in both. Certainly the tendency is to combine the role for cost and simplicity; the companies that do this will ultimately be picking one talent (product or marketing) over the other.
Why is this important? It is important to understand if you are planning to add marketing or product headcount to your team. It also can help drive the content of the interviews you hold with top candidates. Candidates who are answering the tendency of companies to want an "all-in-one" product marketing manager will bill themselves as such. With the right questions however, you can easily discover which tendency rules the way they think.