Me as well. I always use reload but I don't really know how it works. Does it maintain the old and new configs and drops the old after the last connection using it is complete?
When NginX's master process receives the HUP signal[1], NginX will process and test the new configuration. If it is correct, the new configuration will be loaded into new worker processes. The old worker processes will stop receiving connections, but finish their current work. Eventually (within milliseconds usually), all the old processes will be gone and only new processes with new configuration will be working on requests.
[1] On FreeBSD, we just use `killall -HUP nginx` to reload; your distro will probably send HUP to the master process' PID
