welcome to CS (chicken smoothie)! as another user stated, WL stands for wish list. other common abbreviations with trading are TD (true date) and RR (re-release). most RR pets will have an adoption date of Dec. 18 as this is a yearly event where older mote valuable pets are released again to players! typically for higher value pets, TD are worth more than a RR even though they are the same pet.
Here is a thread that is great at explaining pet values and it also has tons of other great info/links!
Forum/viewtopic.php?f=20&t=4899188#p142982064as for your questions about navigating the site, I think taking some time to just click around and open some threads will help you with a baseline! the search function in the top right corner of site is also helpful if you’re looking for anything in particular!