A market manager is primarily responsible for developing a strategic plan for selling her product(s) and/or serivce(s) to her targeted market. This plan includes the "4 P's" of product, placement, pricing, and promotion." She is responsible for implementing the tactical plan, which are the actions taken to achieve her strategic plan. (Look at the strategic plan as a map and the tactical plan as the steps to get from point to point along the path)
A marketing manager must know her market, her customers, their needs and wants, and must also ensure that her sales team is educated and motivated to sell to these customers. It is her job to make sure that her products meet customers needs, are priced competitively, are profitable to the company to sell, and that she filters new customer wants/needs and market innovations to new product development team so that her company can continue to stay on top.
A marketing manager is in charge of collecting and analysing market research, analysing market trends and changes. She is repsonsible for advertising, public relations and communication to make sure her product is well known to her target markets and well presented. She is in charge of branding her product in the marketplace.