`std::async` is a function in the C++ Standard Library that allows you to run tasks asynchronously. It enables you to execute a function in a separate thread, which means your main program can continue running without waiting for the task to complete. This is useful for improving performance, especially in applications that require concurrent operations. When you call `std::async`, it returns a `std::future` object that represents the result of the asynchronous operation. You can use this `std::future` to retrieve the result once the task is finished. This feature is part of the `C++11` standard and is commonly used in modern C++ programming for better resource management and responsiveness.