How do I ping? Why would I do this?

To ping is to send a packet to a computer and wait for its return (Packet Internet Groper). For those outside of IT that doesn't help much.

In practical terms to ping is to notify a website(s) that you have updated your site with new material. This is often done automatically - the excellent Posterous, for example, will update a blog and simultaneously send updates to Twitter, Facebook and other social media sites.