The Minecraft server uses a plugin called Gravy to store your items in a death chest when you die. This is to help both you recover your items and the server not struggle to keep track of additional floating entities.
When you die, your items are safely stored in a grave, which is...your head. When you break it open, your items come spilling out. If a friend or enemy finds it first and breaks it...they're in for a nasty surprise.
Note : You have 20 minutes to reclaim your skull before it vanishes, so don't wait!
Skulls are not free, they come at a cost! You can craft a gravy token to carry with you in the event of death, should you die, it will be used to summon a chest skull where you fell. The recipe will be decided at a later time!