Swing Tags were not originally on Beanie Babies, although that quickly changed, because now all Beanie Babies have one. It usually contains general info, including a poem (If no poem, it usually has lines for your name and a receiver's name), a birthday, and other info. The tags are shaped like hearts.
Swing Tags are recommended to be taken off if the Beanie will be played with by young children (it says so as well on the swing tag), even though it decreases the value of the Beanie dramatically. Cases for the tags came out to help protect the tags so they would not get ruined. They continued to evolve through each year, with a special one for the year 2000.