Post by DrCheis
So if you go to a pet page you'll see an indicator for the pet's Breed. It will say something like #3 B/B
I have no idea what this means. I can't find anywhere on Wowhead that tells me what it means. I'd really like to know how these breed names are derived, but I'd also really like for Wowhead to say this somewhere in case I forget. Here's a screenshot of a relevant example:
http://img191.imageshack.us/img191/9518/capturempb.jpg
Post by Nathanyal
This should help you understand.
I would try to explain it but I haven't played since the end of Cata, so I don't know anything about them.
Post by perculia
The breed you have selected is what is shown in yellow on your screenshot. The breed you mouseover is shown on the right. So in the screenshot, you have Breed 3 selected yet are hovering over Breed 12. If you weren't hovering over any breeds, you wouldn't see any Breed info to the right.
The percentages give a breakdown of a Breed's stat distribution. Breed 3 gives you a balanced boost to all three stats. Breed 12 gives your pet more health, but slightly less of the other two stats.
There are 10 possible breeds a pet species can get. Store-bought pets always consistently have one breed per species. Wild pets can be available in multiple breeds. Depending on your pet composition and enemy team, some breeds may be much better than others. Breeds affect your pet's stat breakdown, along with level (1-25) and rarity (Poor-Rare).
The B/B notation was actually a popular user request, as it's used on several add-ons that display a pet's breed in the in-game pet journal. The numerical notation was also used as it's how WarcraftPets shows breeds on their Battle Info pages.
User Cymre also wrote a guide to Breed IDs on Wowhead's guide section:
BreedIDs for the Serious Pet Battler. It's a great guide that explains the B/B notation, calculations for each breed, and what pets get breed variation.(##RESPBREAK##)2##DELIM##perculia##DELIM##