Mana

Mana is usually reffered to as the cards placed in your Mana Zone (placed below your Shield Zone, Deck, and Graveyard). Mana is normally used to summon Creatures and cast Spells.

Mana Cost
The Mana Cost (seen in upper left-hand corner of a card) is the amount of Mana needed to use that card. In order to pay the cost, you Tap cards in your Mana Zone until the amount reaches the number on the card. However, the Mana used must include at least 1 Mana from the same Civilization as the card you are about to use.

Mana Value
The Mana Value of a card (seen at the bottom of the card) is an upside-down number that indicates how much mana that card is worth while in the Mana Zone. As the cards in the mana zone are flipped vertically, the mana value can be seen the correct way up by the owner of the card. Although there are some exceptions, the Mana Value of a card is normally 1.

Mana Zone
The Mana Zone (placed as said above) is where cards are placed upside-down to pay a Mana Cost. There is no restriction as to what Civilizations can be in your Mana Zone. On each turn, it is optional to place a card here. If you do, you may only place 1 card here at a time unless dictated by a card effect.