What does the 'async' keyword signify in a function declaration?

The 'async' keyword in a function declaration signifies that the function will return a promise. When a function is declared with the 'async' keyword, it becomes asynchronous, meaning that it can perform operations that might take some time to complete, such as fetching data from a server or reading files. By returning a promise, the async function allows developers to handle these operations elegantly, enabling the use of the 'await' keyword within the function to pause execution until the promise is resolved or rejected.

Using 'async' enhances readability and reduces the complexity often associated with traditional promise handling, such as chaining '.then()' calls. Essentially, this keyword changes the way the function behaves, ensuring that its result can be accessed through promise-based syntax.

The other options do not accurately describe the purpose of the 'async' keyword, clarifying the function's role as a promise-returning mechanism rather than affecting execution flow synchronously, privacy, or error handling directly.