Hot bar

The hot bar is a selection bar which appears on the bottom of the screen. It is where you keep and select your items (Wood, obsidian, etc.). It is not your complete inventory, instead it is just a few slots of items that you can select.

Usage
If you want to put more items in your hot bar, simply open up your inventory (Defalt key: E, Y on X-box.), and then drag any item you want to your hot bar. The hot bar has a limited amount of items you can select. That depends on your device (computer & X-box 360: 9 slots, iOS IPad: 6 slots, iOS iPhone: 3 slots, Android: 6 slots, View Sonic: 5 slots, XPERIA Play: 6 slots).