The inventory in TFC differs somewhat from vanilla Minecraft, to expand on its functionality.
Crafting grid Edit
When first starting TFC you will notice that the 2x2 crafting grid has a grayed out section for 3x3 crafting. Once a crafting table has been constructed, it is immediately consumed to open up the full 3x3 crafting grid in the inventory screen. Upon death, the 3x3 grid will be lost, and a new crafting table must be constructed.
Aside from the vanilla armour slots, quivers can be equiped to carry arrows and javelins. They are placed in a slot on top of the player portrait to the right of the chest armour slot, see screenshot above. Some items are simply too heavy to carry in your inventory, ie. the anvil and sealed barrels and large vessels, making the player immobile while they have it in their inventory. These items can instead be strapped onto the back via the same slot as for quivers for the player to regain mobility.