An Item is the basic object/element of the game. Without the Items would be no clothes, no dragons (The big, mountable ones), and no tools or fruits, garbage etc.
There are 3 types of items:
1. Clothes, this includes staffs and others;
2. Mountables or Companions, same thing;
3 And backback items, that includes the rest of the items: Tools, Gems, Fruits, Garbage, Potions etc..
There are unattainable items like:
The moderator shirts, Sheriff's Outfit, some of the NPCs clothes and acessories. But these are only a little part of what the list says.