It's fine, I actually had no idea what pansexual meant until I came to college. Basically it means that you consider the individual's mind and heart foremost, not the body they are housed in or their gender identity (like if they're transexual or intersex). Some consider it an "updated" definition of bisexuality, since many bisexuals define themselves as falling in love with a person, not their body, but some, like myself, feel more comfortable with one label or another (I prefer bisexual).

Wikipedia's definition can be found here, and is quite accurate.