It's consumed during room searches and while playing mini-games. One unit of energy is restored per 3 minute interval. You can also restore some or all of your lost energy by using items from the Energy Boosts tab of the Store.
Each time you search a room, interact with a character at a location, play a mini-game, or complete a quest you get experience points. When you reach the required amount of points, you advance to the next level. With each new level, your energy is completely restored, you get diamonds, access to new rooms and mini-games, and meet new characters.
You get coins as a reward for searching rooms, completing quests, interacting with characters at locations, completing mini-games, and trading in collections.
They're used for purchasing unique items in the Store. You can get 5 diamonds for leveling up, increasing your mastery in rooms, mini-games, and for finding Al Capone's Safe. You can also buy them at the bank.