Barely part of this payment world but still used by many sites to transact, you won’t often find them in a peer-to-peer space but we mention them because they are used in the backend of some of our clients systems
Authorize.net is a payment gateway service provider that works with your existing merchant account to accept credit cards and electronic checks through your website.
The service allows you to provide your clients with a professional payment option that doesn’t require exiting to a third-party site, lending credibility to your business. The service offers mobile payments, phone payments, and E-Commerce solutions.
For retail locations, Authorize.net offers virtual POS or Point Of Sale that allows you to connect a card reader to your computer for transactions in your store.