This is an Interfit 43" (109 cm), White/Black Backing Umbrella. White umbrellas are used to bounce light onto a subject. They provide softening, with soft shadows. Light loss is usually ~2 f/stops compared to the same light used direct, bare light. The black backing cuts down on stray light.
Use this size umbrella for a 2 - 3 person 3/4 length portrait.