Teacup is a term used by (not so good) breeders to attract buyers. I couldn't find the site I was looking for but here is an explanation
Teacup Yorkshire Terrier For Sale - Beware. Coronado Yorkies,* Yorkshire Terrier Florida, FL
Since it is on petfinder, I am not sure. I thought that petfinder was an adoption agency but I feel like the wording of that description is a bit weird. That puppy is sooo adorable though and I could be completely wrong. There are a few YTers who rescue Yorkies. Hopefully someone will give them a reference. Here is a site I found if you are interested.
YTCA RESCUE, INC