Gender identity: The difference between gender, sex and other need-to-knows

"Harry Potter" author J.K. Rowling made waves with her recent tweets about trans women and gender identity. The pictured flag represents the transgender community.

(CNN)Controversial comments made by "Harry Potter" author J.K. Rowling have sparked another online discussion about gender identity.

Rowling came under fire over the weekend for a tweet in which she mocked a headline that read, "people who menstruate."
"'People who menstruate.' I'm sure there used to be a word for those people," she tweeted. "Someone help me out. Wumben? Wimpund? Woomud?"
    Amid the backlash in which Twitter users accused her of transphobia, Rowling doubled down on her initial comment, saying that "erasing the concept of sex removes the ability of many to meaningfully discuss their lives. It isn't hate to speak the truth."
    The phrase "people who menstruate" was intended to be inclusive of women,