In WordPress terms a ping is a “this site has new content” notification that invites search engine bots to visit your blog.

When new pages and posts are created it may take some time for that new URL to be indexed by search engines (depending on the site’s crawl rate). By default, WordPress pings one pinging service called Ping-o-matic, that service will in turn ping others. To speed this up, WordPress offer the chance for you to add update services within the WordPress Dashboard > Settings > Writing.

Ensure these are in the list:

http://blogsearch.google.com/ping/RPC2
http://rpc.pingomatic.com/
http://rpc.technorati.com/rpc/ping
http://www.feedburner.com/fb/a/pingSubmit?bloglink=http%3A%2F%2www.yourdomain.com/
http://rpc.twingly.com
http://api.moreover.com/RPC2
http://api.moreover.com/ping
http://www.blogdigger.com/RPC2
http://www.blogshares.com/rpc.php
http://www.blogsnow.com/ping
http://ping.feedburner.com
http://ping.syndic8.com/xmlrpc.php
http://rpc.weblogs.com/RPC2
http://blo.gs/ping.php
http://www.pingmyblog.com
http://geourl.org/ping

*This ping list was last time updated on 20th November 2013.
*New ping list for 2014 is available on this link.

Why this is good for SEO?

Having your site indexed is fundamentally the most important thing for you. If a URL isn’t indexed it will never be shown in any search engine results page. Not indexing quickly or often enough means your site could miss some big organic search opportunities, especially if your site relies on current affairs or breaking news.