Sure, I can try at least . Secret character is not exactly what I would call them. However, no, I am not hiding anything. I am what is called "Introvert" , meaning: I at times can play along with others, have a good time / fun in doing so. However, I enjoy my own solo time probably more.
This is why I don't want guild members or anyone else I meet along the way to know all my characters. If they know my Main in the guild, that's all they know. My alts are for those times when I am doing things for my account, dailies / weeklies / flashpoints etc.
On an alt, doing missions on some planet out there, I run into someone. we group up for a Heroic or whatever, that person adds me to their friends list. I have logged onto that character again days later, loading screen goes away, I'm now looking at my character and already have a whisper with something like "hey! where you been?"
Cool right? Well for someone who is trying to take a day off from guild stuff, not so cool. I logged onto said character because it was one of those days I wanted to do my own things.
I mean no disrespect to others who like things like this, cool, heck, awesome even! I'm just saying, I am calling this a game breaker for me, not for others, to each his / her own. I need my time to be nobody's guild mate / friend, and I need to know I can safely log onto one of my characters without being investigated by someone in guild or anyone else, that's really all there is to it.