Oh, God, I don't think I could tell you why I began roleplaying. I was 12 years old and got my start on Neopets. I guess it was just something to do, I'd say it fulfilled some sort of fantasy in my head to get behind the eyes of something/someone else, but honestly, I was roleplaying Lupes and Kougras so...yeah, idk, circling back to boredom as far as my 'start' went.
From there, I got into wolves and horses...again, I think it was a mixture of boredom but also the sense of community. I've always been very introverted, so being able to creatively express myself through miniature stories with other like-minded individuals but who would also just chat about their days, share artwork, talk about music, etc. was amazing to me.
Eventually, I wound up getting into Harry Potter genre and never left, lol. Roleplaying became WAY more personal to me from this point on; it was no longer about boredom, but I caught myself inserting a little piece of myself into all of my characters.
Roleplay became very therapeutic to me and remains to this day a way for me to explore things that I've been through (past traumas, etc.), explore things I'd like to do (characters traveling, ideal relationships, etc.). So yeah, I guess in a way it's a way for me to live out fantasies in some ways or explore sides of myself that I probably normally wouldn't explore IRL.
It's also been super self-reflective, has gotten me through some of the harder points of my life (abusive relationships, divorce, etc.) because I'm not the best with words, verbally, but man can I ever get them down onto paper (or into posts, ha). XD Huge example: I entirely don't think I'd have ever come to terms with my sexuality had it not been for roleplay. Exploring various alternatives to all I've known (heterosexuality) through roleplay really helped me in coming out. ^_^
As far as the "second life" thing, I don't really vibe with that. True, I'm way more extroverted online vs. IRL, but I'm always pretty straight-forward and unapologetically me; I'm not pretending to be someone who I'm not OOCly, and I don't put enough of myself into my characters ICly to adopt their personas as my own or someone who I wish I were; I like who I am as a whole and personality-wise, I just like to explore certain situations via RP.