Item Material
Simply hold the item and click the "Item Material" button and it will set to your held item.
Name, Id, Fancy Name
Name is the name that used to identify the item in the .item file and when you edit it, id is used in the item meta data (can be the same as the name it doesn't really matter, the id gets a random uuid generated in addition for the dupe detection), Fancy Name is the fancy item name, with colors and everything.
Lore
Click the "Lore" button to edit the current selected line, right click to remove the current line, shift click to select next line / create it doesn't exists, shift right click to select previous line.
Enchantments
When you click the "Enchantments" button a gui of all the avaiable enchantments will show up, click on any enchanment you want to add and input the level you want it to be, click an added enchantments to remove it.
Flags
Same as the enchantments one but you simply click any flag you want to enable, and click to disable enabled flags.