The interviewer wants to know the scope of your interest in the company and the marketing department. It's common for marketing departments to have a team that comes up with ideas that are then conveyed (with guidelines) to writers, graphic designers, and other members of the department. If they ask this question, they likely hope to hear that you're enthusiastic about contributing to the team in meaningful ways and have a diverse skill set to bring to the table, but if you prefer to focus on the position you're interviewing for, it's okay to let them know that.