I don't use joomla, I find it too limiting - prefer drupal. Here is a link that can give you some info on it:
http://forum.joomla.org/index.php?topic=4364.msg35306
Tag and ping is simply using other bookmarking sites like del.icio.us, furl, blink, and technorati to post links to your web sites under categories you select (tag) and allowing those services to make your link public (ping).
The problem with this method is that people create their own categories or tags, so that a tag can mean more than one thing. And if a tag means more than one thing you are not really getting targeted traffic if someone happens to find your link. Or if your tag is not a familar word, nine out of ten people won't click on it.
example: you have a site that talks about caterpillers (the insect). (silly example, i know). Well one person who likes cats (felines) uses cat as a tag for links to different sites dedicated to animals, the next person (who has a construction business) uses cat to log links to places that sell catapiller construction discounts, another person, who is looking for places to have CAT scans done will use cat to log their finds and so on...
Another way I have seen people use the whole tag and ping deal is to create some tags on the listed above sites (with links to your site) and then put a link on your site to tag that you created on the above site (hope that makes sense). It creates a type of reciprocal linking, I do not know if this practice is considered illegal by google since I have not seen any news or forum posts regarding how google actually feels about this.
hope the above helps