All items and crafted using the crafting square. To craft, simply open the inventory or workbench and follow the 'Easy Craft' instructions. Unless you are playing in Survival mode, most items require blueprints to craft. These can be found on the surface and underground in caves. There is no set order in which a player finds blueprints, but generally depth plays a major role.
An item is anything that can be wielded in the operating hand (right hand of player). Some items are placed like a block but can be walked through, and others that cannot be placed down at all. Most items can be crafted apart from the sledge hammer, which can be bought in Creative Mode and can only be obtained in Dig Deep by killing Spiders . Items can be sold in the Item Shop.
Items include all types of weapons and tools, shields, tools, iron bars, steel bars, ruby gemstones, diamond gemstones, torches, gold pieces, arrows, grenades, and sticks.