What does the await keyword do in JavaScript?

The await keyword is a fundamental part of asynchronous programming in JavaScript when used in conjunction with the async keyword. It effectively pauses the execution of an asynchronous function until a Promise is resolved or rejected. This means that the line of code containing the await expression will not proceed until the Promise has been settled, allowing for a more synchronous-like flow of code, which can enhance readability and maintainability.

When you utilize await, it ensures that any subsequent code that relies on the results of the Promise will operate only after the Promise has settled. This behavior allows developers to write cleaner and more comprehensible code, avoiding the callback hell that often accompanies traditional promise handling using then() and catch() methods.

The other options do not accurately capture the functionality of the await keyword. For instance, it does not execute promises in parallel; instead, it makes the code wait for a promise to resolve. It is also important to note that the await keyword can only be used inside functions that are declared with the async keyword, which differentiates it from some incorrectly suggested functions. Lastly, await does not define a new promise; it merely acts upon an existing promise.