Once the contract has been set, the game can begin. The player who first named the suit that ends up as trump plays the hand. For example, if the bidding goes like this:
North 1 heart
East 1 spade
South 2 clubs
North 2 diamonds
South 4 hearts
West, North and East all pass (3 passes in a row and the bidding is over)
The contract is now set at 4 hearts played by North/South. They will need to make 10 tricks. (base 6 + 4 = 10). North bid hearts first so he will play both hands for this team.
The player (East) to the left of North plays out the first card. North’s partner (South) then lays down his cards face up on the table a column of cards for each suit with the trump suit (hearts) to his right. South is called the dummy for this hand. North will play both his hand and his partner’s (South) hand. North will study both hands and plan his strategy on how to make the necessary 10 tricks to fulfill the contract.
The East/West team will try to make 4 tricks, thus preventing North/South from getting enough tricks to make their contract.
Author, Beginning Bridge by the Numbers