"Async" refers to asynchronous programming, a method that allows tasks to run independently without waiting for others to finish. This is particularly useful in situations like web development, where a web browser can load content while still responding to user actions, making the experience smoother and more efficient. In an async environment, functions can start a task and then move on to other tasks without blocking. For example, when a JavaScript function requests data from a server, it can continue executing other code while waiting for the response. This leads to faster applications and better resource management.