What is the backpack and how do I get one?

The backpack is a wearable item that adds a separate storage section of 10 slots to your inventory. It goes into its own fifth equipment slot, and its contents live behind a tab on the inventory screen.

How to get one. Research it at the workbench, then craft it.

What you can't put in it. Personal items can't be placed in the backpack section.

Resources are spent from it automatically. When something costs materials, the game takes them from the backpack too — you don't have to move anything out by hand before crafting.

When your character dies, the backpack and everything inside it drop as a single container that anyone can loot. When you log out, the section stays with the sleeping body and can be looted there behind a second tab, just like the rest of the inventory.