The Brief: NB and enby are shorthand for non-binary.

DEEP DIVE
NB and enby are an abbreviations for “non-binary.” These terms refer to someone whose gender does not adhere to the gender binary of man/woman or male/female. Other non-binary gender terms include agender, genderqueer, and bigender.
People who are non-binary may use the pronouns they/them/their, xir/xem/xeir, ze/zir/zem, she/her/hers, he/him/his, or a combination of one or more pronouns. The best way to figure out which pronouns to use for someone is to share your own and politely ask for theirs.
NB people can be trans regardless of medically transitioning or not. Trans people can be trans AND binary w/ and without medically transitioning.
Intersex people can be trans, cis, non binary. gender is complex as hell but just b/c it isn't your experience don't make it invalid— Love Trans People (@IndyaMoore) December 10, 2019