It is likely that Vendors you use in Bionic are already set up in QuickBooks. However, the 2 platforms don't necessarily know which ones are the same. The process of mapping will enable to you instruct which Bionic vendor is the equivalent in QuickBooks, and vice versa. And in the instance that a Vendor in Bionic isn't in QuickBooks, you can set it up with the click of a button.
When you first connect with QuickBooks, you should complete an initial mapping before processing data or updating any settings. This will ensure the transfer of bills and payments is seamless once you start processing financials. When complete, you will only need do mapping for new vendors you work with as they come along in the future.