I'm not gay, but the best answer I ever got about the definition of what gay is was from a close gay friend. He said before he figured things out he tried dating girls and had "functional" sex. In other words, he found that sex with a girl could be arousing and everything worked fine. However, he found that emotionally he fell in love with men and he was never able to develop that bond with a female.
When he fantasized about the perfect date and romantic music, he saw himself enjoying the company of a man, not a woman. He simply could not picture a woman in a relationship. Girls were like sisters to him, and it was awkward and odd to consider them potential mates.
While you might have a physical attraction to men, consider that most of relationships are indulging with a person you really like in terms of communication. Sex is a part of that, but it's not the only deciding factor. Who do you want the relationship with? That's the question to start with. The rest will follow.
If you're aroused by men, as you grow older you might need a very open-minded partner to help you deal with this part of yourself since it may continue to be a need. If that's the case, don't hide your feelings or be ashamed - be honest with your partner. There's a huge spectrum of sexuality and people are very different from couple to couple. And since you're a teen, I'm going to tell you the same thing I tell my own kids - love should never be separate from sex. If you want great sex have great love first. It adds great nobility and beauty to intimacy, and you'll feel deep harmony if you do things in that order.