Okay, we have this

//LocalizedNameString, UnlocalizedNameString, TextureNameString, CreativeTabString, MaxDamage, MaxStackSize, ToolTypeString, ToolLevel, isFull3D, LoreArrayString
mods.content.Item.registerItem("Content", "content", "content_item", "misc', 50, 1, "pickaxe", 2, true, ["I am the tooltip text", "I am also!"]);

What's the difference between LocalizedNameString and UnlocalizedNameString? What LocalizedNameString do?
CreativeTabString - how ta add a new custom tab?
TextureNameString - should it be "texture.png" or just "texture" ? Where should I put it?
How to make item have correct name, not item.UnlocalizedNameString.name ?