Difference between product manager and product marketing manager

From Pragmatic Marketing blog

The survey result show that product managers are more inclined to research the market and write requirements while product marketing typically plans go-to-market strategy and writes collateral.

A PM listens to the market; a PMM talks to the market.

Typically the title "product manager" is used to signify people who listen to the market and articulate the market problems in the form of requirements. And the title "product marketing manager" is usually assigned to those who take the resulting product to the market by defining a product marketing strategy. (I actually use the title product manager for both of these). Yet clearly, this delineation is not consistently applied. PMs and PMMs are both equally involved in writing business cases and researching market needs.

And what about marcom? Marketing Communications (marcom) is a service department to product marketing, focusing on the execution of the product marketing strategy. Marcom specializes in programs such as web, direct mail, trade shows, and collateral production. Product marketing knows which of these programs to run; marcom knows how to execute them.

In Crossing the Chasm, Geoff Moore defines and recommends two separate positions:

"A product manager is a member of either the marketing organization or the development organization who is responsible for ensuring that a product gets created, tested, and shipped on schedule and meeting specifications. It is a highly INTERNALLY FOCUSED job, bridging the marketing and development organizations, and requiring A HIGH DEGREE OF TECHNICAL COMPETENCE and project management experience. A product marketing manager is always a member of the marketing organization, never of the development group, and is responsible for bringing the product to the marketplace and to the distribution organization. ... It is a HIGHLY EXTERNALLY FOCUSED job."

Moore goes on to say, "Not all organizations separate [the two positions], but they should be... the type of people who are good at one are rarely good at the other."