What are promises in JavaScript and how do you use them?

<!-- BEGIN COPY / PASTE -->
        const myPromise = new Promise((resolve, reject) => {
            const success = true; // Simulate success or failure
            if (success) {
                resolve("Operation was successful!");
            } else {
                reject("Operation failed.");
            }
        });

        myPromise
            .then(result => {
                console.log(result); // "Operation was successful!"
            })
            .catch(error => {
                console.error(error); // "Operation failed."
            });
        <!-- END COPY / PASTE -->