This may sound like a stupid question, but what's the difference between someone who is a close friend, and someone who is your "girlfriend" or "boyfriend"?

A friend is someone you hang out with, someone you share thoughts with and someone you can rely on.

But isn't that also what a "boyfriend" or a "girlfriend" is as well?

If you hang out with a girl extensively, doesn't that essentially make her a "girlfriend"? Do actions speak louder than words, or am I missing something here?

Sex and commitment = girlfriend. No sex nor commitment = friend.

Actually, sex without commitment could mean she's just a friend "with benefits;" I've had a few of those. The commitment thing is the real deal-breaker.

Getting someone to commit...I guess that's the hard part eh?

Well, getting two people together who are ready to commit at the same time is the hard part. i've been the one wanting-the-commitment end and the not-wanting-it end. When both want it simultaneously, that's yer boyfriend/girlfriend magic.

Haha, I've still got a lot to learn. I'm a relationship noob.

This is all about etymology, the history and development of words. It's very hard to define what girlfriend might mean although most people using it may assume it is to do with a friendship with a female with overtones of sexuality. It may be used when spoken to say girl - friend which simply means a girl who is a friend or it may be spoken as girlfriend which is heard as a girl who is a friend with sexual overtones.
It always used to be used to express a friendship with a girl with the possibility of engagement and marriage.
Language is a living developing experience.

The good guy in me wishes you well. The selfish jerk worries that, once you start getting laid, you'll lose all interest in this little web site of yours.

Girlfriend = sex
Friend = no sex, but still hang out

Stay outside of the friend zone if you're interested in a girl. Once you're locked in the friend zone, you rarely get out.

There is some truth in all of the above responses, but I'd add one more thought. Girls (and/or women) who call other girls "girlfriend" are usually not talking about sex and/or commitment, isn't that a no-brainer? And guys that call other girls "girlfriend" usually mean sex-plus-commitment . . . . also fairly obvious. But a guy can have a friend who is a girl with whom he has no sex and/or commitment, and the term "girl friend" may still be applied, though its meaning is different. As Owen says, particularly in reference to this case, it is a matter of semantics or word usage. One often has to ask for a clarification from the speaker using the word this way. Many sit-coms on TV portray guys and gals who want to move from one of these definitions to the other, and usually it creates comic results.