"Pinging" refers to a "stimulation" of the search engines to draw their awareness to the fact that there has been an update of content on a website so that they can send their robots to index.

If you are using Wordpress as your content management system, pinging service to limited search engines is pre-installed on it. However, some marketers still go ahead to add other search engines to the pinging service to draw the attention of many of such engines to any update of content.

Pinging services such as Pingomatic are also sometimes deployed externally for the same purpose of drawing attention of search engines to an update but in some cases an update of backlinks so that the backlinks can be indexed very fast.

Nothing just telling search engines that a page has updated. Now come and have a look on the page.

U can do it using

pingfarm.com
pingomatic
bulkping.com
pingdevice.com
Scrapebox etc.

As already explained, pinging a search engines tells it to come and index new articles.
I personally like bulkping and pingler for pinging.

By default Wordpress (if you are using Wordpress) only has one service that it pings when you post content (pingomatic.com)

You can add other sites to this list to ensure they also know about your new content.

Here's a link to a post I wrote which explains it in more detail but also shows how you can easily update your ping list with over 90 more 'ping' sites to ensure your new content gets indexed quickly:

Get Indexed by Google Fast by Updating Your WordPress Ping List

Nothing to buy and no opt in, I'd just appreciate a like/bookmark etc if you found it useful

Libby