No, pinging is not the same as submitting to a directory or a search engine. Submitting is done to get initial entry into their database - to let them know you exist. That needs to be done first
A ping is a term that was related to sending a request to a computer on the network to see if it received it and responded. There are lots of kinds of pings.
Pinging, when related to blogging, is the process of sending a message to an aggregator, directory, or whatever, that you have posted a new message.
There are many sites that can be pinged.
See
http://pingomatic.com/ for an example. By pinging there, you can automatically ping several sites at once.
Write an item, publish it on your blog and then go to Ping-O-Matic! to let all the others know you just published something.
A new service has been added at
http://FeedBurner.com that will automatically ping several services for you if you run your feed through them.
See
http://www.feedburner.com/fb/a/publishers for more information about their services and
http://www.feedburner.com/fb/a/publishers/pingshot for specific details about PingShot.
I have all of my feeds going through their service -- for free -- and I just added PingShot to each feed. I also added the blog via email provided by FeedBlitz.com (see the publishers page at Feedburner for more info). Now, someone who prefers getting email can subscribe to my blog feed using the form on my blog. See the right column at
http://johndilbeck.blogspot.com for an example.
Now, when I publish an item, it is written to an index page, it's own page, emailed to subscribers, and PingShot notifies the aggregators that I've just done it.
It takes some time to understand and set up, but it's more than worth the effort to make it all work automatically.
If you visit
http://Feedburner.com and read the information they provide, you'll learn all about pinging.
All the best,
JD