Queer, historically, is a slur used to call gay people strange disturbing and unnatural. Like most slurs, some people have tried to reclaim it. In the 80s during the AIDS crisis there was a lot of shock-and-awe activism tactics going on to draw attention to how gay men were dying and the government was being very slow in addressing the epidemic. This included the use of the word queer as a reclaimed slur, as it was being used extensively as a slur at the time. Not all people were in favor of reclaiming it.

Additionally around this time and especially in the 90s, post modernism was taking hold in academia. This is a philosophy that believes in 'multiple, conflicting things being equally true because universal truth does not exist'. In many ways, the pioneers of this academic field attempted to appear as edgy as possible, and thus explored slur usage. They decided to study sexuality, but opposed the idea that sexuality is concrete and unchangeable. They believe it is fluid and subject to change since there are no universal truths but rather 'everyone's identity and experience is supposed to be equally true', which depending on who you ask, can be seen as very progressive or incredibly homophobic.

They decided to call this theory of sexuality 'queer theory' and positioned themselves as academics guiding the activists — to be progressive is to consume Butler and Foucault. To be repulsed by the idea of telling gay people they are queer (overwhelmingly a slur at the time) and their sexuality is changeable is to be backwards, even if you were grassroots gay activists.

Queer theory expanded into theories of gender as well, finding best friends in defining reality based on identity not material circumstance. Queer theory does not get along with materialism.

Post modernism is really popular among the left and most universities now. It is the party line, so to speak. Other forms of leftist thought based in materialism are considered backwards and outdated. As a result, the key tenets of post modernism have been embraced, such as word salad and incomprehensible, undefinable 'truths'. Thus, queer theory, in which sexuality and gender are completely opt in, and how the word queer is used in it, as a way to refer to all those they choose to define as 'not normal', becomes in vogue.

Thus, queer became a progressive identity standing for nothing other than the idea of counter culture sexuality and gender as per postmodernism thought. Theoretically, it is supposed to mean those who are attracted to the same sex (the ones the slur originally was applied to) and those who do not conform to sex stereotypes (which was often gay people, and is the reason trans people, who were often homosexual, became associated with gay people in the west in the first place). However, it is widely used in the queer theory notion of simply refering to anything not within the 'mainstream'.

Nowadays, it is still used as a slur quite extensively. I have heard it myself. However, the general public consensus is that it is fully reclaimed and can be used by corporations and people who were not the target of the slur, because academia proclaimed it the most progressive way to talk about people considered 'not normal' regarding their sexuality or whether they conform to the stereotypes associated with their sex.

People have wildly different opinions on the use and meaning and usefulness of the word. However, the above are some basic facts regarding its history and usage. Altogether, I think one has to decide what it means and what they think of it for themselves. There is no concrete, real meaning, since it is commonly now used as a post modernist term, and a 'concrete, real meaning' is the antithesis of post modernism. It also has history and modern use as a slur. How it is used as a post modernist term is also something you could choose to judge as progressive or backwards. It is up to you, op.