If you have been playing the Resident Evil Village Maiden demo you will have realised two things. First, it is scary. This goes without saying. Secondly, there is a necklace in there that you might be confused about.
When you first crawl up the ladder and out of the dungeon, the first room you find yourself in has a bone necklace on a table. You can pick it up, and as you wander around the house trying to escape you will notice something. The necklace does not have a purpose.
Everything else you can find in the demo definitely has a purpose. Items will allow you to progress through the level, by either opening doors or giving you access to new areas in other ways. Notes will give you little bits of information that could safe your life, usher you towards progress, or just give you interesting bits of information about the denizens of this cursed place.