Good question.
To oversimplify, bisexuality generally refers to people who are attracted to multiple genders. Whereas pansexuality generally refers to people who are attracted to other people without regard to gender.
For bisexual people, gender may be an important factor in sexual attraction.
For pansexual people, gender may be a less important factor for sexual attraction.
(Edited for a tiny bit more clarity. Please refer to comment chain below for more thorough discussion of bisexuality. I should also mention I’m a cishet man so take my comment with a few thousand million grains of salt.)
I disagree with this explanation (as a bisexual person).
It is all semantics and the labels sort of bleed into one another, but I prefer the definition laid out in Anything That Moves: The Bisexual Manifesto:
Bisexuality is a whole, fluid identity. Do not assume that bisexuality is binary or dougamous in nature; that we must have "two" sides or that we MUST be involved simultaneously with both genders to be fulfilled human beings. In fact, don't assume that there are only two genders. Do not mistake our fluidity for confusion, irresponsibility, or an inability to commit. Do not equate promiscuity, infidelity, or unsafe sexual behavior with bisexuality. Those are human traits that cross ALL sexual orientations. Nothing should be assumed about anyone's sexuality—including your own.
It goes onto say,
There are as many definitions of bisexuality as there are bisexuals. Many of us choose not to label ourselves anything at all, and find the word 'bisexual' to be inadequate and too limiting.
That's fine. I don't judge people for identifying as pansexual. However, there is a twinge of discomfort, pain, and of being once more made invisible whenever it is claimed that one must be pansexual to be attracted to people outside of the socially constructed gender binary. The oft-stated "hearts not parts" line insinuates, to me, that bisexuals are not interested in those aforementioned hearts, and it circles right back around to the stigma that bisexuals are sex addicts incapable of fidelity or love.
I call myself bisexual because it is more comfortable for me. It has always made more sense. My definition would be something more akin to: attraction to people of genders like one's own and attraction to people of genders dislike one's own than anything to do with two genders.
The manifesto also says:
We are angered by those who refuse to accept our existence; our issues; our contributions; our alliances; our voice. It is time for the bisexual voice to be heard. Do not expect each magazine to be representative of all bisexuals, for our diversity is too vast. Do not expect a clear-cut definition of bisexuality to jump out from the pages.
I'm aware you made it clear these were general definitions, and it is difficult to easily explain the intricacies of sexuality sometimes. These are simply some of my thoughts on the matter.
Generalities will always leave out crucial, important nuance. Sorry if I was reductive and flattened your experience into a simple category.
It's ok. I just find it incredibly reductive, and I've had pan "friends" before criticize, scrutinize, or outright label me pansexual without my consent because I'm not just into strictly men and women.
It's ludicrous, imo. This definition necessitates that bisexuality is inherently transphobic, or at the very least demands that self-identified bisexuals show no attraction towards people of non-binary genders. I don't identify that way and almost every bisexual I know does not identify that way. It is, in my experience, an external definition thrust upon bisexuals by others, and often by pansexuals themselves in order to differentiate themselves from the transphobic, exclusive bisexuals.
It really boils down to semantics, I think, and it's not really a fight worth having -- is pansexuality valid, is it another form of bisexuality, is it completely distinct in some meaningful way -- but I take some grievance with the idea that bisexuals writ large harbor no attraction to peoples of nonbinary genders.
It is most certainly not ok for me to be reductive. Especially about identities that are not my own. Seriously, thank you for the insight.
It depends on who you ask. There's a lot of discourse over what these words mean and if they even mean different things. The only thing everyone agrees on is the flags, so you're bi if you really like purple and pan if you're more of a CMY printer person.
Which color scheme you prefer,
or 
. Otherwise they're the same thing.There isn't one really. I find that pansexual people tend to describe themselves as "gender blind" aka not really taking gender into consideration when thinking about dating whereas bisexual people tend to still have a preference. This is just my experience and definitely not true for every bi/pan person. As a bisexual person I still personally have a bias towards femininity as opposed to masculinity.
At the end of the day it all comes down to which label you prefer. No one really has the right to tell you how you can and can't identify, provided it's not identifying with Nazism or something similar of course.
From my experience, pan people identify as attracted to all genders while bi people identify as attracted to both sexes.
