bisexuals are attracted to two or more genders, and they could have a preference or not.
"Bisexuality is a complete and fluid identity. Do not assume that bisexuality is binary. In fact, don't assume that there are only two genders."
Bisexual Manifest (1990)

identifying as pansexual means that gender plays no role in that person's sexuality and that they don't have a preference for one gender over another. it’s a genderblind sexuality.

they are different sexualities and both are valid. they coexist and don’t erase each other so there’s no reason for invalidation towards any of them. if you still don’t understand please search and be open to learn and get educated.

articles that i used and may help you