Payflow is PayPal's version of authorize.net. Payflow is the gateway but the processing is done by your merchant account. So, you will need a "real" merchant account from a financial institution like a bank to use payflow.
Unless you are doing a good deal of volume this might not be the best way to go because, while you are charged a couple of points less on the processing fee, you are usually stuck with 2 monthly statement fees (payflow and your merchant account). Compare the different paypal options here:
https://www.paypal.com/us/cgi-bin/we...ile-comparison