The Functionality template std::async runs the purpose f asynchronously (most likely inside a independent thread which could be a Portion of a thread pool) and returns a std::future that could ultimately maintain the results of that purpose call. 1) Behaves as though (two) is termed with plan remaining std::launch::async std::future https://alphawireless.com/future-proofing-american-utilities-why-900-mhz-is-critical-for-utility-communications/