The Collectibles screen in story mode.

Collectibles are special items which can be collected, but do not have any extra carry-weight. Once found, collectibles can be 'examined' at any time through the Journal.

In story mode, collectibles come in various forms; the most common are single page notes, which can be read, as well as keys and other items.

In Survival mode, collectibles come in two types: notes and cairns.

A Note Left BehindBuffer MemoriesClimber's journal page