Salvage

Salvage is essentially a form of currency in the Survivor Timeline of Tomb Raider. It is used for crafting weapon upgrades

Tomb Raider
It is commonly found in the form of small yellow wooden boxes, but salvage can also be found when looting dead enemies. looting Hidden Tombs, and in large grey metal containers that must be payed open. With the right skills learned, extra salvage will be rewarded, and will even be able to be taken from dead animals.

Salvage is used to upgrade Lara's weapons, in the form of weapon modifications, which will increase damage, firing speed, accuracy, ammo capacity, draw time, and hold time.

Multiplayer
Salvage also plays a part in the Multiplayer Mode, it is used to purchase playable characters and weapon upgrades.

Rise of the Tomb Raider
Salvage is a gatherable common resource in Rise of the Tomb Raider.