Originally the term to ping someone was a technical term. When you ping someone you are checking their Internet connectivity. Pinging makes sure that their is no extended lag time between when something is sent to the person, or from the person, and when it is received. Now when you want to ping someone it means to check to see if they are online. This is often done by sending an instant message. If there is no answer to the message, a nudge, an email, and a phone call may be the next step.