A more thorough explanation:

Definition: Past consideration refers to an act or promise given by the promisee before making a promise that is sought to be enforced. It is not considered as consideration for the new promise because it has not been given in exchange for this promise. However, there are exceptions for new promises to pay debts barred by limitations or debts discharged in bankruptcy.

Example: If a person helps their neighbor move furniture without any prior agreement, and later the neighbor promises to pay them for their help, this promise cannot be enforced because the consideration (helping move furniture) was given before the promise was made.

This example illustrates that past consideration cannot be used as a basis for a new promise. The act of helping move furniture was not done in exchange for the promise of payment, so it cannot be considered as consideration for the new promise.