OEM (Original Equipment Manufacturer) manufactures the components or the products that will be bought by a company and then sold under the purchaser's brand name.
ODM (Original Design Manufacturer) is responsible for designing a product and also the production of the product.
OBM (Original Brand Manufacturer) is a company that retails their own branded products that are either the entire products or component parts produced by a second company. They sell the goods under their own brand name in order to add value. The OBM will be responsible for everything including the production and development, supply chain, delivery and the marketing.