Janelle Monae comes out as Pansexual

[Fuzzy Necromancer]

Is there a meaningful difference between Pansexual and Bisexual or are they synonymous?

It's a bit complicated. Current definition is pansexual means "attraction to all genders/regardless of gender" while bisexual means "attraction to same and other genders" or "attraction to more than one gender." Bisexuals are more likely to, for example, be into fat women but prefer skinny guys. Some people feel pansexual fits them better. Some prefer bisexual because, even though it's not always just two genders, it has a history.