Value refers to how much something is worth. Sometimes that is in money, sometimes in the amount of care is given to it, and sometimes in a point system.
Consider making a value guide for the following:
The cost of different items
Ranking of how close the friendship is of different characters
How many points each enemy type is worth
The system of money in a world
What can be traded for something else
Ranking of books, episodes, or movies
Rarity level
Attack power / Health points
Difficulty to unlock or discover