B2B stands for business to business, which means a business (maybe yours?) that sells its products or services to other businesses as opposed to consumers.
Note that B2B refers to the final purchaser of the product or service rather than the distribution channel. For example, if you make a food product such as salsa that is sold in stores you are not B2B, just because you are first selling your product to a distributer or a store, both of which are businesses; you are a B2C business because that’s who ultimately purchases your products.
B2B examples include business software, corporate legal services, office equipment leasing, and corporate gifts. There are examples of companies that are both B2B and B2C, for example, chocolate companies that sell through retail as well as corporate gift markets.
Some sources of financing just focus on servicing B2B businesses.