Pansexual means bisexual, pretty much. There are a few differences, which I will quickly go over, but they basically mean the same thing for most people's purposes and the differences are a lil' complicated.
Bisexual - attracted to men, women, and others.
Pansexuality - attracted to anyone, regardless of their label.
To put this in perspective for a heterosexual (which I assume you are?) um, think about the way you are attracted to men, the male parts of them like muscle, shoulders, beards, etc. and then, think about the way heterosexual men are attracted to women, like their breasts, hair, those are the only two things I can think of, I'm sure there are other things. Bisexual people are attracted to men and women in the same way. Pansexual people are attracted to people, but in a different way. Secondary sex characteristics (breasts, build, muscle mass) don't factor in to the way that they are attracted to people. They feel attraction... differently.
For example, you might look at Chris Hemsworth and think "damn, what an attractive man" and so would a bisexual person.
But a pansexual person would look at Chris Hemsworth and think "damn, what an attractive person." because his gender is insignificant in their minds
And the difference between bisexual and pansexual people is pretty insignificant, unless you are one, for intents and purposes, they means basically the same thing.