A JavaScript Promise is an object that represents the eventual completion or failure of an asynchronous operation. It allows developers to write cleaner code by handling asynchronous tasks, such as fetching data from a server, without getting tangled in complex callback functions. A promise can be in one of three states: pending, fulfilled, or rejected. When a promise is fulfilled, it means the operation was successful, and it can return a value. If it is rejected, it indicates an error occurred, and an error message can be provided. Promises can be chained together using methods like `.then()` and `.catch()` to manage multiple asynchronous tasks effectively.