I think they are just charms you put on the bottom of wine glasses to tell which one is yours. What we were going to do is put these charms with different color beads on the water glasses set at the table. Our colors are ivory and purple, so I was going to set up 1 person at each table to get the purple charms. With this, the DJ will announce that whoever is in possesion of this charm, they will win the bottle of wine we are using as part of our centerpiece.
A few years ago I was at a wedding that did this. The favors were wine glass with the bride/grooms names and wedding date. They used them as seating cards by placing them at the tables with wine charms that spelled our first names. So, it was obvious that they were ours to keep. They were very cute. Even if you don't get wine glasses as favors, doing personalized favors is a little extra something that lets them know they can keep them.