Photography is one of those careers where the industry is so broad that realistically you can select any field to focus on. Even if you define yourself as a particular type of photographer, you can further niche yourself into one of the many subcategories that are available in almost every genre.
For example, if you are a fashion photographer you can further categorize yourself as catalog, high fashion, fashion blogger and/or editorial. Portrait photographers can focus on maternity,... more (link is external)