The word "ping" is derived from the acronym PING, which stands for "Packet Internet Groper" (no kidding!). According to Webster's New Millennium™ Dictionary of English, a ping is designed "to get someone's attention with a sharp sound or other form of communication". The ping I'm talking about is the Internet equivalent of that kind of ping.
Most blogging software will ping other blogs automatically whenever a new article is posted. Those that don't can be made to do so by using third-party solutions. As I explained in a guest article I wrote for Pearl at Interesting Observations, pings create pingbacks. A ping is created either by a link within a post or by a specific trackback to a trackback URL that isn't a link within a post. Either type of ping will normally create a pingback on a receiving blog. What does the pingback do? It gets the attention of the author (and only the author if the ping isn't to a specific post) and the readers of that site.
Within the last 2 days, my blog received pings from 2 other blogs that I'd never been to or even heard of. Each one mentioned a different, specific blog article. I have all my comments emailed to me (I don't receive the comments for other authors like my guest author, Hari) and I received the pingbacks as comments in my email. Not being familiar with either blog, I simply had to go check them out.
Stalkk.ed
The first one I visited is called "Stalkk.ed". It's an interesting name, but I couldn't get beyond the article itself to investigate it. What a find this was! It's a list of 100+ WordPress plugins, articles and resources. I checked a couple of them out and I'll definitely be going back for more. Enrico Bertini linked to my article about WP_PingPreserver.
Needless Productions
The second one I visited is called "Needless Productions". Ryan Edmunds weighed in with his opinion on RealRank, SocialSpark and PageRank and linked to my article about SocialSpark, PayPerPost, RealRank, Google and You.
The value of the pings
By linking to my articles, both blogs have produced backlinks to my blog and are driving traffic to it. In return, my pingbacks produced backlinks for their blogs and this article will produce more. That's how Internet linking is supposed to work. Placing "rel=nofollow" attributes on links like this (which are unpaid links) defeats the purpose of organic linking in the search engines. Some bloggers are doing this and I think it's a HUGE mistake.
[...] to read his posts even when I barely have a clue what he's talking about, like this one about Packet Internet Gropers. There always seems to be a lively conversation about Pagerank, or the legalities of pirated stuff, [...]
[...] The Value of a Ping: from RT Cunningham of Untwisted Vortex. At first I thought I was looking at a golf post, and then I wondered if it was the 'ping' command he was talking about, but it turns out to be about ping backs from other blogs, including a couple he'd never even heard of linking back to his site, and the resulting traffic, and, more importantly, the new information from the other sites, that was generated. [...]