No implications that you'll notice, honestly, especially since you're in First. In Coach, they can affect things like upgrade priority (if you're eligible for them at all) and same-day change processes. For the most part, though, this isn't a part of your ticket you go out looking for during purchase.

At a basic level, this is just how DL manages seat inventory and pricing. Some of the higher fare classes (which are what the letters represent) may be refundable or flexible, but you'll probably notice that feature more explicitly during the purchase process (those big "Flex your fare" up sell boxes).

Generally, most expensive to least expensive fare classes are FPAG for first class and YBMSHQKLUTXV for coach.

But again, once you've purchased your ticket, these letters don't make a huge difference in your actual travel experience.