What does it mean when a transaction is sided by bank 2b?

The transaction on the 2b side of the bank is a business-to-business electronic transaction.

According to the query of relevant public information, the bank's C-side refers to software designed for individuals and is oriented to personal accounts at the customer's discretion, while B-side products are oriented to enterprises and are bank-to-bank business.

Transaction refers to bartering, and later generally refers to the buying and selling of goods, also known as "trade".