The refinery is the place where, once per turn, the active player can drop in any card from his hand, therefore sacrificing it and transforming it into an energy resource. Upon sacrificing that card, he will draw a new card from his Library. Energy resources are then used to play cards on the battlefield. Used energy are replenished at the start of the player’s turn.
Each card has a cost to pay in order to use it. This cost is payed using the player’s resources every turn. Looking at the left image, you’ll notice 3 orange orbs around the refinery. That indicates the active players has 3 available resources to play a card or a combination of cards for a maximum of 3 resources.