Items

Items are objects that can be collected and equipped in Portal 2, however they are only available in Co-op mode. There are four categories of items: Hats, Miscellaneous items, Skins and Gestures. When collected, items are stored in the player's Backpack automatically. Items can be purchased from the Robot Enrichment Store, or are automatically collected if the player is eligible to receive them, for example if the player owns specific compatible hats in Team Fortress 2. (As of May 2018, you can no longer transfer hats from Team Fortress 2 for unspecified reasons)

Hats
Hats, also known Headwear, are items that can be equipped in the "Head" slot of the loadout screen. Hats are only used for aesthetics, and do not prove any benefits or advantages in regards to gameplay. Hats can be purchased from the Robot Enrichment Store, or could've be acquired automatically if a compatible hat is already owned by the player in Team Fortress 2.

Miscellaneous Items
Miscellaneous items are items that are equipped in the "Misc" slot of the loadout screen. Similarly to hats, Miscellaneous items are only used for aesthetics, and do not prove any benefits or advantages in regards to gameplay. Miscellaneous items can be purchased from the Robot Enrichment Store, or will be acquired automatically if the player has owns any of the Potato Sack games, and played the game during the Portal 2 ARG.

Skins
Skins are items that are equipped in the "Skins" slot of the loadout screen, and change the default textures of Atlas and P-body. Skins, like Hats and Miscellaneous items, are only used for aesthetics, and do not prove any benefits or advantages in regards to gameplay. Skins can only be acquired by purchasing them from the Robot Enrichment Store, with the exception of a small number of Skins that were made available as part of some individual Portal 2 pre-order promotions.

Gestures
Gestures are items that are equipped in the "Gesture" slot of the loadout screen. They are special animations which players can activate during Co-op gameplay. A number of Gestures are made available to all players by default, and additional Gestures can be purchased from the Robot Enrichment Store.