Wasn’t this question asked not that long ago? Maybe I’m thinking of another site. “Queer” is a reclaimed slur and is used by some LGBT people to label themselves, e.g. the term “genderqueer”. It can also be used as a catch-all for any orientation or gender identity that isn’t straight/cis, thus the Q covers anything that isn’t specifically LGBT but is still not straight/cis (things like intersex, asexual, questioning, etc.)