exploration points are needed to explore the treasure zone. you can obtain more exploration points by using exploration potions, which you can obtain either by purchasing it with diamonds, or through some events.

you can check your exploration points and get more by:
-From the Player Info Screen tap on the player icon on the upper left side of the game screen.

-you can see the exploration points bar, click the "+" sign next to it

-From there, you can explore other ways to obtain more of this item.