If you are interested in knowing the cost breakdown of your ticket, it's clearly shown on your emailed confirmation. A receipt can be resent sent to you, if you can't locate the original, which shows the detailed info on the purchase, including taxes and fees. Just complete the three boxes on the form found here:I don't know where the fee comes from. They sw said it $20 in taxes. That's all I got. No clarification from any of the 3 agents I spoke with.
https://www.southwest.com/air/manage-reservation/index.html?clk=GSUBNAV-AIR-MNGRES
Looking at one of my receipts from a paid flight, not booked with RR points, I see the following:
Excise Taxes
September 11th Security Fee
Segment Fee
Passenger Facility Charge