A thenable is a promise-like object with a then() method. This term is used to indicate a promise that is foreign to the particular promise implementation in use. This feature allows us to build chains of promises, allowing easy aggregation and arrangement of asynchronous operations in several configurations. Also, if we don't specify an onFulfilled() or onRejected() handler, the fulfillment value or rejection reasons are automatically forwarded to the next promise in the chain.
