Queer is a complicated and "radical" term that has been used disparagingly, an outside of the binary way of self-identifying, and an umbrella term to describe sexual/gender minorities.
Queer Historically Seen as an Insult:
The word Queer has typically and historically been used as an insult to gay men and lesbians, it is considered a synonym to "strange", "unusual", and "different" and has been on par with hateful rhetoric such as "faggot", "dyke", "shemale", and "he/she".
Reclamation of the Term by Sexual Liberation Movement:
Queer as a Sexual/Gender Identity: