Shelves are blocks added by the Shelf 1.2.5. mod, one of the mods on the Yogbox created by Risugami. This block allows you to display up to 9 items in it, which will be shown to the world. To get into them you just right click one and put items in it.
It is quite simple to craft a shelf. It requires three of the material of choice.
Because of their small size, a crafting table is not required to make them.