Hey a random use for my degree.

Gender is based on how you feel about yourself, obviously different than sex, which is based on your chromosomes. Each culture has a different idea of what gender means. For example, the US is a mostly patriarchal culture, meaning men are mostly in charge with some exceptions (this is SLOWLY changing to a more equal culture) compared to a matriarchical culture where women are mostly in charge with some exceptions. This puts pressure on people for how men and women are expected to act.

Gender performativity is how you perform your gender. I don't want to assume your gender, so just think about the things you do to feel more like your gender. For some men, this is buying a muscle car or BBQing or going to the gym. These are stereotypes of masculinity, but they show how men purposely try to perform gender. For men who don't do these things, they're called girly or feminine.

(bonus lesson) -Rhetorical questions- What does this say about American culture? If not performing the "man" gender results in being calling a different gender, what's wrong with that? Why is being called girly or feminine considered a bad thing? The US spotlights masculine identities without spotlighting the gender itself, therefore making feminine traits less desirable without explicity saying so. The US have moved away from overt misogyny into subtle misogyny in order to appear more equal. It gives plausible deniability.

The meme specifically is referring to how much harder trans people have to "perform" their gender compared to people who were assigned their gender at birth.

Might be referring to philosopher Judith Butler's "gender performativity." Guessing by the similar name, I don't know what it actually means.