To a first approximation, they describe the match or mismatch between a person’s gender identity and their assigned gender at birth (AGAB).
“Cis” = “my gender identity matches my assigned gender at birth”
“Trans” = “my gender identity does not match my assigned gender at birth”
The question being asked is, “Given that when you were born they thought of you as a (boy/girl); are you now expressing or experiencing a (male/female) gender, or a (female/male) one?”
Logically speaking, this is an xor operation; it asks if two things are the same or different. If boolean variable a represents your AGAB and boolean variable b represents your gender identity, then “are you trans?” is a xor b — is your AGAB different from your gender identity?
Again, this is to a first approximation. There are people who don’t fit binary labels, and so an xor operation on binary labels doesn’t fit them either.