This is the bowl the libations are poured into. It's not necessary if you are fortunate enough to be able to celebrate outside, because the wine can be poured right onto the ground, and the cakes can be tossed into the bushes for the critters. But if you are inside, it's a necessity!
During the circle, all food and drink that is consumed is first shared with the Gods by putting some into this bowl; so keep that in mind when you choose one. (It's also a good idea not to look into it, if you have a great variety of food. And sometimes we add Tums for the gods.....)
After the ceremony, the bowl must be emptied outside, in a ritual that we know in our tradition as "Cold Feet," because that's what you get when you go outside barefoot to do it! The bowl is raised towards the moon, and the participants, once again, give a blessing or dedication such as, "As the Gods share with us, so too do we share with the Gods," and the contents of the bowl are emptied onto the ground.
However you do it, the contents should eventually wind up outside, on the Earth, to show that we realize that is where all of our food comes from, and that we are grateful.