This short piece - billed as 2 pages, but there's nothing more than a Dungeons & Dragons 4e logo on the second page - looks at a frequent result of getting injured: bleeding. In game terms, 'bleeding' occurs when the damage taken is such that there is ongoing blood loss per round after the one in which the blow is struck. Of course, it's not only blood loss, the same can be applied to any bodily fluid necessary to the well-being of the creature in question.
Elementals and constructs are immune to this effect - although there's arguments for allowing elementals to 'leak' and constructs to lose oil or some other liquid mecessary to their function. However, a new feat called Gaping Wound allows you to inflict damage that'll cause bleeding on elementals and constructs, so you can indeed have that water elemental leaking all over the floor provided you invest in the feat.
It's a neat way of explaining ongoing damage, and remind characters that you cannot always wait until the end of a combat to check on the fallen and attend to their healing. As for the feat, useful if you expect to meet up with a lot of constructs or elementals.