Minecraft wiki entry for Beginner%27s_guide, associated text: Below these are the 27 slots of your main inventory. You can drag items around from these slots to your hotbar and back, armor pieces can be moved to and from their armor slots, and items can be dragged to the personal crafting grid, about which more below. Dragging items completely out of the GUI's rectangle and releasing them there drops the items into the world, much like the Q key (or whatever you rebound that to), but it is easier to drop a whole stack this way.