Bi means two, and pan means all - but I've met a lot of bi people that would date outside of the gender binary, so is the difference really that simple? I'm sure I could fall into either category - depending on how you define it, of course. Is there more to it? I'm not really sure, so I'm sorry if I'm being kinda ignorant! I still need to find out though.
Well, human sexuality is incredibly complex so, I don't think you should worry too much about it. If you like someone regardless of their gender identity, well that's great! Don't label yourself!
Pansexuality is a useless label imo, It's only there because of semantics. Plenty of bi people date anyone.
I agree with Creativemind. Although when talking to other bi's it can be more interesting to say you're pan to avoid confusion. But to anyone else I say I'm bi.
Someone asked a bunch of pan and bi people why they defined themselves the way they do and read out some of the reasons in this video: I know one bi person who uses bi because (in her words) she's not attracted to trans people and she considers pansexuality to include attraction to trans people. For me, though, I'm pan because I'm attracted to people regardless of their gender. I do sometimes use bi for convenience, but "pan" feels more right and accurate.
I completely agree with all the points in the video Hats provided above. I think bi or pan people each have their own definition for their sexuality, and the word choice usually comes down to your own definition and how comfortable you are with either term. Me personally, I chose bisexual because it sounds better to me, and I am attracted to the same gender and other genders, but not necessarily all genders.