Ahh I see. To ping someone means to instantly get their attention. It sends a notification as well as a link to the post that mentioned you this way.
I'll ping you real quick so you can see first hand how to receive one.

Twigg:

In order to ping someone else, you just go "@"username; (without the quotes around the @). You HAVE to put in the username exactly how it is displayed on menewsha, though. The ping process is extremely picky.