This command lists all of the items in the inventory of your current target. Use 'player.showinventory' to list all of the items in the inventory of your character.
showinventory Target Command
This command would print a list of all the items in the inventory of your target. To select a target, click on an NPC or container (in the game) whilst the console is open.
This console command would print a list of everything in your character's inventory (because the command is prefixed with 'player.').
INV is an alias of the ShowInventory command - it has the exact same function.