Board Thread:Magnus Chase & the Gods of Asgard/@comment-24098124-20180726234609/@comment-36853616-20190110110108

In the book, Alex says she's "genderfluid and transgender". Does she mean that she was born a girl, but has very male days, born a boy but is female most of the time or something else entirely? I was really confused about this, can someone tell me what she means when she says this?