The Board is made of several distinct zones. The mainboard, your deck, your graveyard, your hand, your lava counter, your life point counter, and the turn timer.
The mainboard has space for 7 cards to be summoned at any one time.
Your deck is made up of exactly 30 cards, when you run out of cards you will not lose the game immediately, but you will stop drawing cards.
Your graveyard shows all the cards you have played in this game. Both players can see all cards in either graveyard.