How do I know if I'm gay or bi?

I really don't know if I like girls. I am definitely gay, but I'm not sure about bi. I was at a party and nearly made out with a girl and would do it given the chance, but I don't if I'm just experimental and want to try something or am actually bi. I don't like girl "parts" but I don't know if I'm just close minded about it. Plz halp