When a business sells its products or services only to other businesses then we can say, it is following the B2B model. The full form of B2B is Business to Business. Where a business is selling a product or service, and another business is buying that product or service. Be it small or big, local or multinational, a business requires so many essentials to run. Such as commercial office, billing machine, employee management software, marketing service etc.
The business that is selling these things is the first B or Business of B2B, and the business that is buying these things is the second B or Business of B2B. This is the literal meaning of the term B2B. Transactions between two businesses. Such as transactions between manufacturer and wholesaler, transactions between wholesaler and retailer etc.