What is a pen name and how and when to use them in article / affiliate marketing

Some what confused why do people use pen names in article marketing and affiliate marketing and what other areas are they used and why ?

There's certainly nothing new about it. Authors have been doing it for years.
For a detailed answer, see: Affiliate Marketing Tips: Using Pen Names

Wow...thanks

Great link to a pretty heavily discussed topic on pen names, I have to go back there and read it again, still confused but more clearer because of this link.

I use pen names at Ezinearticles to write in different areas. If you want to be an authority in more than one area sometimes you don't need your name associated with different topics that are completely different. For instance: I have one website on home decorating at http://www.dimedecorating.com and I write articles by Gail J Richardson. I have another website about Grandparents
Rights at http://www.newgrandparentrights.com and I write grandparents rights articles under the pen name of Jacquelyn Dunn.
They are both me. My name is.. Gail Jacquelyn Dunn Richardson. Ezinearticle kinda says to keep it in some form of your name but if you wrote in several names that might be hard to do.. However you can come up with a lot using initials.

G.J. Richardson
Jacquelyn Dunn
Jacquelyn Richardson
Gail J Richardson
G. Richardson
J.Richardson
Well I guess that gives you the idea.