From their website:

The Electronic Transactions Association is the leading trade association for the payments industry, representing over 500 companies worldwide involved in electronic transaction processing products and services. The purpose of ETA is to influence, monitor and shape the payments industry by providing leadership through education, advocacy and the exchange of information.

ETA’s membership spans the breadth of the payments industry to include independent sales organizations (ISOs), payments networks,  financial institutions, transaction processors, mobile payments products and services, payments technologies, and software providers (ISV) and hardware suppliers.