Gender-critical means rejecting the idea that “gender” is an inner feeling and instead seeing it as a set of sex-based stereotypes that society forces on people.
As CurledUpWallStaring puts it, “Gender is assigned, not by a doctor … but by society. They perceive you as female and then they treat you as the feminine gender: babymaking machine, sex object, subservient, emotional, nurturing, soft … This is not a role you choose, but one assigned and enforced through violence.” source [citation:3a86cfc6-f9c6-4d5d-bc29-f16f68868535]

It distinguishes itself from conservative or religious-right positions by remaining firmly feminist.
FineBalance44 stresses that gender-critical feminists “aren’t the same as the religious right. Unless you think the religious right is fighting for abortion, criticising gender roles, criticising the unpaid labour of women, etc.” source [citation:ebf18e62-8f5b-40ab-8917-298b28ca86c5]

It supports trans civil rights while opposing medical transition for minors and defending sex-segregated spaces.
lunitabonita explains: “I still believe that trans people deserve equal rights in housing, employment, and access to medical care … I just no longer believe that medical transition is life-saving treatment … I believe that women and girls deserve separate space from men and boys … That doesn’t mean that I think trans people are inhuman.” source [citation:00563424-f0ea-403f-ace0-5ffdd1cbedb0]

It calls for “gender abolition,” not new identity boxes.
BuggieFrankie sums it up: “The way to go is to eliminate gender entirely. Let people do what they want without any expectations because of what they have in their pants.” source [citation:a2e73dc0-5ffa-4423-b831-1d5f375639bc]

In short, being gender-critical means recognizing that gender is a harmful set of stereotypes, not an identity; defending everyone’s civil rights while protecting children from medical harm; and working toward a world where personality and freedom replace pink-and-blue boxes altogether.