Cosplay is the act of dressing up as a fictional character, especially with considerable fidelity to its presentation and that said fictional character comes from a franchise but in practise it’s blurred with plain old fancy dress and masquerade. At any point whenever there’s a fancy dress party or festival somebody could dress up as a sci fi franchise character.
There’s also causeplay or masquerading for a cause. There are women who whenever they rally they dress up as the titular handmaids from the programme ‘Handmaid’s Tale’. Said programme even spawned a fashion show. This is causeplay in practise as they’re rallying for reproduction rights and stuff.
A similar example is found among Guerilla Girls where they put on gorilla masks to protest the lack of female presentation and female objectification in art museums. Since women are underrepresented in fine arts, one can’t help but wonder if it verifies the cliche of men being more visual than women.
There are also people who dress up as superheroes for charities and stuff but then again they could ‘cosplay’ as any other character, including more generic ones. They can and will dress up for whatever political cause they’re advocating for.