I can't find any information on the Internet about this items so I'm askine here. What are they used for? Are they important?

Not terribly important. They are artifacts and relics and can be handed in to a character called only "Storyteller" in the capital. He will then tell you a story about the items and persons. Or in other cases he will make an item of them which you can use or sell. And you get a bunch of gold and XP for it as well.

Some info about them here, although beware of spoilers:
https://pathfinderkingmaker.gamepedia.com/Relic_Fragments

Often these items are hidden behind Perception checks, so it's not a guarantee you find enough of them for the Storyteller to reward you.

Actually, the specific ones mentioned here is a type you can hand in to the Storyteller (or sell for much less to normal traders). It's nothing important, you just get some money for them. There are different types, like cyclops coins and suchlike.