Is Omni part of Marriott?

Could you clarify the relationship between Omni and Marriott? I've heard the two names mentioned in the same context, but I'm not entirely sure if Omni is a subsidiary, a brand, or simply a partner of Marriott. Could you elaborate on the nature of their association? Are they both involved in the same industry or do they have separate focuses? Is there a common ownership or management structure that links the two? And finally, how might customers distinguish between the services and products offered by Omni and Marriott?