"The Lottery"

I did not like this story at all at first I wasn't quite sure what was going on in my mine a lottery is a good thing. All the towns people rush to be there like its a great thing but now that I look back and reread it a little I find that its not a good thing at all and don't understand why anyone would want to have this kind of a lottery? Everyone in the town had to be there and take a piece of paper from the black box that dated back who knows how long? According to the part stating "Tessie Hutchinson was in the center of a cleared space by now, and she held her hands out desperately as the villagers moved in on her. "It isn't fair," she said. A stone hit her on the side of the head." Shirly Jackson pg 411. I was so appalled that someone would think up this sick game/lottery. From what I understand I guess its good if you don't get to be picked cause everyone gets to throw a rock at you? How long does this go on and every month? Is this a way for people if they have problems with someone to get back at them in some sick way? I guess I am confused at what was the point of this story and who would do such a thing?