Promissory Estoppel is an equitable doctrine that allows for the enforcement of a promise even in the absence of a binding contract or valid consideration, provided that relying on the promise caused a detriment to the promisee. This is primarily outlined in Section 90 of the Restatement (Second) of Contracts, which requires a promise which the promisor should reasonably expect to induce action or forbearance and which does induce such action. To apply this, Alex, imagine an uncle promises his nephew $5,000 if he quits his job to travel Europe. The nephew quits his job (detriment) relying on that promise. Even though there was no formal "bargain" or return consideration that benefits the uncle, the court may enforce the promise to prevent injustice. In conclusion, if you reasonably relied on a promise and suffered because of it, the law may step in to stop the promisor from backing out.