There are many eBoxes on this website. When you open one, you will find a random prize, chosen among the available items according to their chances. If you like what you just found, get it shipped straight to your house, or get the value of the item back as account credit.
Once you deposit a sum on your account, you cannot get it back. Don't worry, though! Just buy a box and then get the prize shipped at your house, or try your luck again with another box if you don't like what you got!