Oh, FFS, Federberg. What does the Q stand for if NOT "queer?" Queen? Quizzical? Quiet? Quinine? Do read the post above by Hailz...she's one of our newest members and very young, if you missed her intro, so she speaks for a younger contingent with her openness and inclusiveness about it. It's a nice, concise explanation.
For the oldsters, I'm not sure who else will answer the above for you, if not me. I'm straight, but live with a lot of gay and gender-queer people in my personal and work life. "Queer" was originally a derogatory that was readopted by the gay community, not so long ago. Some older gay people have a problem with it, but many older, and most younger people embrace it. It can mean binary gay, but it also implies the panoply of non-specific sexual orientation AND non-specific gender identity.
I was talking to a gay male friend about this today, specific to this conversation, and he said the T was originally "transvestite," but now is "transexual." He feels it must be included, as a part of the group, and doesn't see splitting off from the transexuals, as they were always part of gay life. I'm sure you know that it was the "transvestites" (as they were known at the time) who basically started the Stonewall Riots.
I think, (not sure), but the "+" is about enveloping everyone on the queer spectrum. Does that help? I invite anyone to correct my historical assessment or otherwise definitions.