A worker is a process of nginx.. Each process is multithreaded and can handle thousands of connections each. You can have one worker and 50,000 connections to it, but it's good to have at least as many workers as you have CPUs and I usually multiply this times 4 (so 4 worker per CPU).. Worker connections is how many connections each process (worker) can have open at one time (max files open, sockets, etc)