For most people in the film industry, they pick something they are talented at – whether its scriptwriting, directing, producing, acting, cinematography, or editing – and stick at it, slowly working their way up through the business.
Others are not content to simply stick to one discipline, instead choosing to dabble in more than one skill. After writer-directors and producer-directors, one of the most common combinations in the industry are actor-directors, people who are known equally for their acting chops as their skill behind the camera.