Whether you as a Product Manager report into Marketing, Development, or another group, you play a critical role in helping Marketing position and explain the product so that the message resonates with your product's prospects.
The Marketing folks are the experts at taking an image of your software product and polishing it until it really shines. They can make the product message sound truly compelling, and artfully express how you stand compared to the competition.
But except for a minority of exceptional 'marketeers', Marketing is submerged in the day-to-day mechanics of generating the message, the collateral, the supporting materials, and talking to all necessary audiences from media to investors to prospective business partners.
What the Marketing folks don't have, and it's the raw material that they absolutely need to portray the power of your product, is the specific and essential perspective on the business users of your product and why they use it.
Take a look at How Can Product Managers Help Marketing? to see how you as Product Manager--and you may very well be the only one who can do this--can contribute to Marketing in order to make your product's marketing stand out in the busy, crowded, and uncertain software market that we find ourselves in today.