Woot sells one item a day, at very low prices compared to anywhere else. So if you happen to want that one item, then you pick up a great deal. However, they have an unknown set amount of that one product, and as soon as they sell out, that's it. The next item shows up at midnight, and it starts all over again.
However, during a Woot-Off (OMG!!) the items come one right after another, but the next item doesn't show up until the one before it has sold out. So some products are known as Woot-Off-killers, because the product is so unwanted that it takes forever to sell out.
There's all kinds of jargon that has built up around Woot because it's so popular, judging by how fast the items sell out (they just sold 100 $1000 lcd tvs within about 45 minutes), the number of posts that rack up on the items' blogs within minutes, the support sites for it such as
BagsofCrap.com that keep track of past items and how many were sold, and the Wiki article for it and so on. I was surprised I hadn't heard of it sooner, like I said I've only known about it for a month. The whole office is addicted to it, including the boss.