The Lost Relics Encyclopedia is located at the top bar, next to the skill book and it allows you to find information about anything in game (relics, tools, events, bounties, weapons so on).
How to open the Encyclopedia?
You need to unlock the Encyclopedia before you can access it. To unlock it you must finish the starter quests. If you don’t know where the starter quests are, just open the map (TAB or M) and find a question mark or an exclamation mark in yellow. That’s where you’ll find the NPC with the quest.
The name of the quest that unlocks the Encyclopedia is Powerful Knowledge, but you’ll have to do the first quests in order to get to this one.