The Functionality template std::async runs the functionality f asynchronously (potentially in the different thread which might be described as a Element of a thread pool) and returns a std::future that could at some point maintain the results of that purpose connect with. 1) Behaves like (2) is referred to as https://alphawireless.com/future-proofing-american-utilities-why-900-mhz-is-critical-for-utility-communications/