Since we don't live in a perfect world, we have gender. And, being humans who like to categorize and make things fit into tidy little boxes, we group and put labels on things.
I've recently come to realize that I'm genderfluid. No, I'm not some puddle, and you can't use a mop to clean me up (well I suppose you could, but I wouldn't let you). I'm genderfluid: I experience my sense of my own gender as an frequently-changing place somewhere on the gender spectrum; and sometimes multiple places on the spectrum simultaneously; and sometimes I'm not even on the spectrum. Confused? Me, too!