Every promise:
A promise is a commitment made by one party to another to do or not to do something in the future. It is a statement that creates an obligation and is enforceable by law. In the context of the statement, "every promise" refers to each individual commitment made by the parties involved in the agreement.

Example: A promises to sell his car to B for $10,000.

Every set of promises:
A set of promises refers to multiple commitments made by the parties involved in an agreement. It involves a mutual exchange of promises where each party agrees to do or not to do something in return for the other party's promise. In the context of the statement, "every set of promises" refers to the collection of commitments made by the parties.

Example: A promises to sell his car to B for $10,000, and B promises to pay the agreed amount within 30 days of the transaction.

Forming the consideration for each other:
Consideration is an essential element of a valid contract. It refers to something of value that is exchanged between the parties to the agreement. In the statement, "forming the consideration for each other" means that the promises made by the parties serve as the basis for the consideration they receive from each other.

Example: A promises to sell his car to B for $10,000, and B promises to pay the agreed amount within 30 days of the transaction. Here, the promise to sell the car forms the consideration for B's promise to pay the purchase price.

An agreement:
An agreement is a meeting of minds between two or more parties, where they mutually understand and agree upon the terms and conditions of the contract. It is the result of an offer made by one party and the acceptance of that offer by the other party. In the context of the statement, the promises and sets of promises made by the parties form the agreement.

Example: A and B negotiate the terms of the car sale, including the price, payment terms, and any additional conditions. Once they reach a mutual understanding and acceptance of these terms, they have an agreement.

Overall, the statement emphasizes that an agreement is formed when every promise and every set of promises made by the parties become the consideration for each other. This highlights the mutual exchange of commitments that creates a legally binding contract.