Please give me some information about group posting.
I've never come across that term, although a quick Google search would indicate that it's not a widely used term either (either that, or I suck at Google).
Anyway, the best I could come across is posting on Group pages (i.e. Yahoo Groups - if it even exists any more) to get backlinks. Naturally, this doesn't seem to happen that much any more.
You asked the same question two days ago:
In future, if you have a simple question like "What is ...?", the chances are that you can get the answer from Google or from our SEO FAQ – please check these out before starting a new thread here.
If you're touting yourself as an "experienced SEO Specialist and Search Marketer" then you really shouldn't need to ask this kind of basic question at all!