What defines a merchant according to PCI DSS guidelines?

A merchant, according to PCI DSS guidelines, is defined as an organization that accepts card-based payments. This definition focuses specifically on entities that directly handle cardholder information through the acceptance of payment cards for goods or services. These entities are subject to PCI DSS compliance requirements to ensure that the transmission and storage of cardholder data are secured, which mitigates the risk of data breaches and fraud.

The other options represent different roles in the payment ecosystem but do not fit the specific definition of a merchant. For example, entities issuing payment cards refer to card issuers, while service providers that offer payment terminals serve as facilitators for merchants but do not themselves accept card payments. Similarly, businesses that facilitate financial transactions do not necessarily deal with card payments specifically and might include entities that operate in a broader financial context. Thus, the distinction emphasizes that a merchant's primary function is to accept card payments from customers.