Ping is response time for messages to get through to another computer measured in milliseconds. 500ms ping is half a second, which is noticeable ping. Ping doesn't correlate to jittering games though. That is due to unstable and variable internet connection. For example, I always have 400ish ping to all Europeans because of the distance but I have good net so it's stable. Therefore, there is an ever-so-slight delay before orders go through but the game itself runs perfectly fine.
Any ping under 500 is fine for playing IMO as long as the net is stable and won't stutter during the game.
