Trans has become too broad an umbrella to say anything very meaningful about it. The term can encompass
people who hate their sexed bodies and go to great and often painful lengths to change them (previously known as transexuals);
people who dislike the way that society treats them because of their sexed bodies and so look to change the way they are seen so they are perceived as the opposite sex (these individuals may or may not have gender dysphoria and may or may not have a variety of surgeries, hormone treatment but usually won't etc);
people who are escaping abuse or homophobia and see or are told that transition is the answer;
people who are reconnecting to a culture that includes some concept of a third sex/gender or two sexed/gendered individuals (in North America this will usually be described as two-spirited);
people who like cross dressing for a sexual kick (generally older men who while enjoying pretending to be what they think of as woman often really like women at all, sometimes referred to as autogynephiles or AGPs);
people who perceive that it is advantageous to claim a trans identity for a temporary or permanent benefit (whether that is access to a sports scholarship, changing room or prison) but probably have little or no dysphoria of any sort;
people who seem just to like to fuck up other people for a laugh (trolls really, some of whom are really just old fashioned misogynists);
and according to Stonewall people who are simply gender non conforming in any way (so most of us really).
who knows what those who claim they are gender fluid really believe. I've only met two adults who claim to be fluid, both were relatively young males with some history of trauma. One gentle and generally quite thought provoking, a champion of diversity and equality. The other was really just angry.