You should know that MSP is short for MasterCard Service Provider. It is something that companies need to have to be able to resell MasterCard Credit Card Processing using their company’s name. You can find the registered and approved MSPs on the Mastercard Service Provider list. You should also know that Visa has a similar certification for this that is called ISO.
There is an Acquiring Bank or Processor that represents the MSP. They are given a set of terms for their merchant account contracts and allow them to markup the rates for processing and other fees. Even though the processor of the account may be called an MSP, this most often refers to the sales organization that is the middle man between the sales and the account provider.