Some may run commands when clicked, some may store items, some may just be completely uninteractable.
The edge slots are completely uninteractable, cannot run commands nor run items, cannot be clicked nor anything. These automatically generate with Custom Model Data to look cool with the provided texture pack assets.
They are the gray stuff that doesn't even look like a slot
Display slots are completely uninteractable too, but these contain an item of your choosing and its just shown there, looking good.
Pro tip: If you use a MMOItem, changes in /mmoitems browse will be copied over, so you can just edit the item there.
Command slots are basically display slots that run a command if the player clicks them. Its very simple, just like that.
Funny thing is that command slots can also be of storage, such that they may run different commands when the player puts an item in the slot vs when they take it away.
Storage slots admit items to be put inside them; These items may saved in the world, the player's data, or dropped to the ground when the player closes the GUI.
Storage slots may display an item when empty, this just exists visually and is entirely uninteractable, even allowing items to be put on top.
Used container, though it doesn't do much without its mythic skill CJ_Activate:
FruitBlender: NumberOfRows: 2 ContainerType: STATION Contents: - CONTOUR 0||DISPLAY||v LADDER 0||1||NME§b|| - 1||EDGE||v LIGHT_GRAY_STAINED_GLASS_PANE 0||1||NME ||CMD3000|| - ICE 2||STORAGE||v LIGHT_BLUE_STAINED_GLASS_PANE 0||1||NME§bPut Ice Here|| - 3||EDGE||v LIGHT_GRAY_STAINED_GLASS_PANE 0||1||NME ||CMD3000|| - 4||EDGE||v LIGHT_GRAY_STAINED_GLASS_PANE 0||1||NME ||CMD3000|| - 5||EDGE||v LIGHT_GRAY_STAINED_GLASS_PANE 0||1||NME ||CMD3000|| - 6||COMMAND||v GREEN_STAINED_GLASS_PANE 0||1||COCgoop mythicmobs runSkillAs CJ_Activate %player%||NME§a§lActivate!|| - 7||EDGE||v LIGHT_GRAY_STAINED_GLASS_PANE 0||1||NME ||CMD3000|| - CONTOUR 8||DISPLAY||v LADDER 0||1||NME§b|| - CONTOUR 9||DISPLAY||v LADDER 0||1||NME§b|| - 10||EDGE||v LIGHT_GRAY_STAINED_GLASS_PANE 0||1||NME ||CMD3000|| - ICE 11||STORAGE||v LIGHT_BLUE_STAINED_GLASS_PANE 0||1||NME§bPut Ice Here|| - 12||EDGE||v LIGHT_GRAY_STAINED_GLASS_PANE 0||1||NME ||CMD3000|| - FRUIT 13||STORAGE||v DEAD_BUBBLE_CORAL_FAN 0||1||NME§7Blender Blades|| - 14||EDGE||v LIGHT_GRAY_STAINED_GLASS_PANE 0||1||NME ||CMD3000|| - 15||EDGE||v LIGHT_GRAY_STAINED_GLASS_PANE 0||1||NME ||CMD3000|| - 16||EDGE||v LIGHT_GRAY_STAINED_GLASS_PANE 0||1||NME ||CMD3000|| - CONTOUR 17||DISPLAY||v LADDER 0||1||NME§b|| DisplayTitle: <#DB3C3C>&lFruit Blender