Pansexuality means being attracted to someone's personality, not someone's gender. Bisexuality is being attracted to both males and females.
>>5, it is true that we can be biologically male or female, however in some cases the line in biology blurs. XXY may mean that the person exhibits male sexual organs but also displays some female traits (slightly developed breasts etc). Some people even have both sexual organs (this is called being intersex), though this is rare.
Also, some people may not feel like their gender. They may be biologically male, but they feel female. This is called transsexuality. Transgendered people feel like people of the opposite sex despite being born with the organs they have.
You choose how you want to identify yourself. In the case of bi/pansexuality, are you attracted to people's personalities or do looks play a part, even a little?