There's a difference [Read the description!]

(2018 update. Hoooo boy) And in my opinion, that difference is that bisexuality exists.
Sorry, I only think there are two genders.

UPDATE (11/5/2020) : I didn't really appreciate the snarky description that my younger self left here, so I want to update this with an accurate description of my opinion, this time more fleshed out with sources to back up my claims.

I completely disagree with this stamp. I'm neutral on the gender debate, but that's not necessarily relevant because bisexuals can be attracted to non-binary people. I'll let the 1990 Bisexual Manifesto do the talking:

“Bisexuality is a whole, fluid identity. Do not assume that bisexuality is binary or duogamous in nature: that we 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.”

Adding onto this, bisexual people can also be attracted to transgender people. I'm biromantic and I'd be willing to date anyone regardless of gender.

After having a bit of a relay run from Freud's definition in 1917 to that of the BDSM community in the late 20th century, the baton was passed onto this modern definition of pansexuality, first used in 2002 in this LiveJournal post:
i-am-pansexual.livejournal.com…

I want to draw your attention to this excerpt:
“Pansexuals love people of all genders, male and female, but unlike bisexuals, pansexuals love transgendered, androgynous and gender fluid people, people who don't fit into the categories of male or female.”

This description of pansexuality exactly matches the meaning of bisexuality. Pansexuality has been defined this way as either based on the misconception that bisexuality only includes cisgender men and cisgender women, or made to replace bisexuality as its more "inclusive" counterpart. Either way, the use of the pansexual label contributes to bisexual erasure. The two terms mean the same, but what we know today as pansexuality was appropriated from bisexuality.