Until buyer's agency came into being, technically no one represented the buyer. Buyer's agency is created by a separate document called a Buyer's Broker Agreement, which is signed prior to writing a purchase contract. This is an employment contract, just like a listing agreement. Be sure you know what you are signing before you sign anything. You could be bound to that agent for the length of time specified in the agreement.
Dual agency exists when the designated broker represents both the buyer and the seller.
Both parties to the transaction are being represented by the same designated broker. The responsibilities to remain fair, honest, and ethical remain. Both agents must disclose anything that may materially impact the transaction. If the agent knows the property is going into foreclosure or that the buyer is willing to pay full asking price plus for the home, this information cannot be disclosed unless permission is granted in writing. The real estate agent must remain fair and impartial, giving neither side a negotiating edge.