Bandages are a Health item in Rise of the Tomb Raider and Shadow of the Tomb Raider. They work similar to Medipacks in the Classic Tomb Raider, LAU, or the Lara Croft Games, but unlike in those pre-reboot games they have to be crafted from resources found in the games.
Rise of the Tomb Raider
To craft Bandages, the player has to press and hold the LB (Xbox One and 360) or L2 (PS4). Bandages do not actually appear in the inventory; instead Lara starts wrapping a piece of cloth and some herbs around her arm and when she finishes, her health is back to full. This takes about two or three seconds, enough time to get killed by an enemy, so one should take cover if at all possible.