In Queer contexts, fluid refers to one’s sexual or gender identity in which things change or fluctuate over time; that is, a sexual or gender identity which is not static or fixed, or, that they can be subject to change unexpectedly.
Examples may be genderfluid/genderflux, or various bisexual+ identities. Many people may not realise their fluid identities until they actually experience it; for example, a heterosexual or homosexual person may enter one, or many, bicurious phases throughout their life.
Bisexual+ people may find that their attractions towards certain genders increase or decrease on a fluid basis.
Fluidity should not be confused with bisexuality being a “phase”, nor homosexuality or heterosexuality as something that something that can be changed through intervention; nor should it be considered a “transitional” period between identities; rather, it should be seen as a distinct.
One’s own personal fluidity is not applicable to other sexual and gender identities anymore than any other identity is (e.g. the existence of heterosexuals does not diminish the existence of homosexuals or bisexuals; nor do genderfluid people diminish the existence of transgender or cisgender individuals – and vice versa).