A pansexual individual is someone who experiences sexual attractions to people regardless of gender identity, in practice this is very similar to bisexuality.
Pansexuality differs with bisexuality in that most people who identify as pansexual are attracted to people in trans and nonbinary communities. This doesn't mean that some bisexuals aren't (many actually are and use pansexual and bisexual interchangebly) however some bisexuals are attracted to be only cis gender males and females.
In practice bisexualty and pansexuality overlap
In practice pansexuality may also vary in that it includes more than two genders but not all (despite its prefix meaning all). For instance, because of its inclusion of nonbinary and transgender individuals some people who are exclusively attracted to nonbinary and trans people may still identify as pansexual despite the fact they are not attracted to cis people. This contradiction exists because it is impossible to label every variation in human sexuality. The best way to know is to ask. Pansexuals like bisexuals can also have preferences.
Also while pansexual is defined as a sexual attraction, colloquially people use it to include romantic attractions as well. Its often times used to mean panromantic, while this is incorrect, the concept of romantic orientation is not as widely known as sexual orientation and most use it out of convience or out of genuine ignorance, there is a difference.
Girl 1: I thought you were a lesbian why are you sleeping a trans guy?
Girl 2: I'm pansexual, im sexually attracted to multiple genders!