The pen name. Le nom de plume. Il nome della penna. El nombre de la pluma. And the question -- should I have one or not?
There is only one quick and easy answer, and even then, it's not that easy. Answer? It depends on what you want out of your writing.
Do you want complete anonymity? To protect your private life from the outside word? Then, yes, you'll want a pen name. But I guarantee you, at some point, someone will find out the truth. Ask Stephen King about that one; when no one knew who the hell Richard Bachman was and then got outed as a pen name of Steve! But still, separating your professional life from your personal life is a good plan -- especially when it comes time to brand that name (which is another discussion and that will come later).
Do you plan on writing in several genres? Then, you definitely need to have a pen name -- or several. A different name for each genre. That branding thing again. I think pretty much everyone knows by now that I write under my own name of Jesse V Coffey, but I also write under the pen name of Siobhan MacKenzie. The reason being, Jesse V Coffey writes paranormal, historical, and speculative fiction. But Siobhan MacKenzie writes contemporary romance, romantic suspense/thriller, and erotica. One day, I want to write a series of thrillers and I'll have another name for those. I keep them separate because Jesse's readers are not that interested in Siobhan's writing. And vice versa. So, cross-genre writing will be best served with pen names.
Maybe you don't want your family to know you're writing erotica, erotic romance, or porn. Pen name. I know a couple of authors of BDSM novels that have pen names.Why? Because they keep their writing life away from family life -- to keep them from reading something that might distress them.
Or, maybe you just want a pen name because you want one. Okay. Again, your choice. But the point it, it depends on you. There is no right or wrong answer. Just what your comfort level is and what you hope to get out of your writing. Once you make that decision, then go for it.
Are you an author? Do you have a pen name? Why did you choose it? Tell us about your experiences and help fellow authors with that decision.