Here's my dad's take on it:
They sell one item only each day. When it's gone you have to wait until the next day before you see what new item they are selling. It's always a good price, and each day the item is different.
Sometimes they have a woot-off and change the item about every ten minutes, and sometimes they have mystery bags of stuff. You pay $5.00 for a bag and wait to see what you get. My friend John says his son's friend got a flat-screen screen tv. No, it didn't fit in the bag, but there was a redeemable certificate in there.
Anyway, it isn't about the stuff - I find the ad-writer's prose to be laugh-out-loud material.
Plus, there are lots of other features there if you explore a bit, like this particular bit of what they call Flickr Roulette. And given how much I enjoy and shill for Flickr these days, I figured I had to include this link as well.