Payment Service Provider

Payment Service Providers sit in between companies (eg webshops) and payment methods/banks/card schemes. So as a webshop, instead of having to integrate with a bank to do transfers or with PayPal, you only integrate with the PSP. A lot simpler to do, and instead of having to chase each individual payment method for your money, the PSP will handle that for you. They can also provide additional services like a unified dispute view, credit management, small loans, etc...