A Product Manager is responsible for all aspects of a product from development, to product communication, to product budget management. In general, a Product Manager is responsible for the strategy of a particular product a company offers.
Product Managers work with several other groups within the company including, but not limited to, Product Development, Marketing Research, Marketing Communications, and Finance.
In preparation for an interview as a Product Manager, it is helpful to have a solid understanding of the company's product line, the industry it competes in and the customers it serves. In addition, be prepared to talk about products in general - some that you think are designed or marketed well and others that you think have room for improvement. Since analytical skills are important, be prepared to explain how you would utilize these skills for strategic decisions as a Product Manager. Hiring managers will want to get an understanding of your decision making process when dealing with challenges. Be prepared to clearly communicate your process and why you chose that process.