Queer: General term for gender and sexual minorities who are not cisgender and/or heterosexual. There is a lot of overlap between queer and trans identities, but not all queer people are trans and not all trans people are queer. The word queer is still sometimes used as a hateful slur, so although it has mostly been reclaimed, be careful with its use.
People who identify as queer may feel that their sexuality is too broad and/or too fluid to narrow down, and that the only way to describe it is as not being straight. They may experience attraction to certain people only under certain circumstances, at different intensities, and for any number of time. For example, a queer person could be attracted to only guys for a while, then only non-binary people, then both, then neither, and so on. The possibilities are endless, and each person experiences their identity in their own way.