As requested from a viewer, here is a quick overview on how to create craftitems and some of the different things you can do with them. Some of the concepts presented aren't very practical, but could be extended to do something that would make sense.

minetest.register_craftitem('new_mod:example', {
   description = 'example',
   inventory_image = 'default_dirt.png',
   groups = {tree=1, sand=1, wood=1},
   on_use = function(itemstack, user, pointed_thing)
      local hp = user:get_hp()
      user:set_hp(hp*2)
      local pos = user:get_pos()
      minetest.set_node(pos, {name = 'default:dirt'})
      itemstack:take_item(1);
      return itemstack
   end,
})