Christmas trees are great and all, but having to keep a half-dead tree alive in your house by crawling underneath and watering it every day really sucks. It's not like you can actually keep the thing alive; those needles are going to be everywhere by new years whether you like it or not.
Might as well make tree life support a little easier. This thing might look like a big present, but it's really just full of water. A tube runs from it into the tree's water reservoir, keeping it hydrated so you no longer have to deal with watering it on a daily basis. Just be prepared for a really disappointed kid when he opens this thing up Christmas morning and finds a few gallons of tepid water rather than the PS3 he asked for.