It's lunchtime at your local kindergarten classroom. Billy is sad. Johnny is sad. Sarah is sad. Why? Because their parents have packed them food that they don't really want. Billy doesn't really want his apple. This week all he has been getting is apples and is sick of them. 
Johnny, his mom has been packing bananas all week long and is sick of them. He doesn't particularly want his banana today.
Sarah is also sad. Her mom has been packing carrot sticks even though Sarah keeps telling her mom that she doesn't want carrot sticks. She's sick of them. But he mom told her, "Don't argue. You better eat your carrot sticks. If we don't finish them, they'll go bad."
Well, as you can imagine, it so happens that Billy, Johnny, and Sarah eat their lunch together. 
Now, for adults, it might be complicated for them to figure out how Billy, Johnny, and Sarah are going to sort things out so each of them get what they want. But for Sarah, its easy. She gets an idea.
Sarah draws a circle on their table with pencil. And, well, can you guess what happens next? She says. "Okay, let's put what we don't want to eat in the circle and trade."
She puts her carrot sticks in the circle.
Well, even though Billy doesn't want carrot sticks, he is interested in seeing what Johnny might put in the circle to trade. Billy puts his apple in the circle, wondering what he'll get to choose from in exchange.
And, can you guess what Johnny does? He puts a banana in the circle.
Can you guess what happens next? Hmmmm?
Billy takes what he wants of the three items: a banana, Johny takes what he wants: carrot sticks, and Sarah takes what she wants: an apple.
They eat lunch, everybody getting what they want.
The next week, they do this every day. More kids see what they are doing and decide its a good idea. At, some tables, things don't work out whereby everyone gets what they want. Sometimes there are arguments. Eventually the teacher notices. She gets an idea. One day, just before breaking for lunch, she says:
"Okay, class, I see that you are using sharing circles to trade lunch items. That's great. But it seems sometimes there are arguments because not everyone gets what they want. Why don't we have a sharing circle for the whole class so that people can have a greater variety of choices. In this way, people are more likely to get what they really want. And if you leave extra food that you don't want, people who forgot their lunch can have something to eat. Let's try it."
Now, this teacher has thought this though. She has brought some typical food items that the kids usually eat and has put them in the trading circle on a table at the front of the class, so as to increase the chances that everyone will be able to get what they want and lessen the likelihood of there being any arguments.
What ends up happening is that kids come to the front of the class in a more or less orderly fashion, see what is available for trade and what they might want and then have a chance to decide what they are willing to trade for the item.
The teacher keeps track of who leaves what and who takes what to make sure no one abuses the system and praises the kids who leave extra food for kids who don't have any. The kids are good, they learn not to take more than what they want and leave what they don't want for others who might be in need.
Everyone gets what they want and there is always leftover food for kids who had forgotten their lunch, to the point where, some food has been left on the sharing table at the front of the class so long the teacher worries that it might go bad.
So every couple of days, she checks to see what might be going bad and takes it and gives it away to poor kids who whose parents can't afford to send them to school.
