What is an umbrella term? Well, it's a term that covers a range of different subjects. Kinda like an umbrella.
'Transgender' is an umbrella term in itself. It covers most of the gender dysphoria situation. So when I say "I am transgender", it doesn't necessarily mean I want to be a girl 100% of the time. Most of the time, yes. But I would describe me as mostly non-binary, or genderfluid. The only problem with that is that nobody seems to take either of those terms seriously. The term 'transgender' is fairly popular. A lot of people have mixed feeling about it, but it's still a thing that most people recognise. So that's why I stopped saying 'non-binary' or 'genderfluid'. I would explain it, only to have people continue to use address me by my naturally born sex.
Clearly, it wasn't working. So I switched tactics. And so far, by saying 'transgender', people are much more careful with how they call me. The drawback here, however is that the term 'transgender' begins to lose it's real meaning. While, yes, it is a term meaning someone who feels as if they have an invalid sense of personal identity, it does also mean someone who feels they were born into the wrong body.
I think it's kind-of obvious that I'm not 100% trans, since I don't insist on people referring to me as a girl, nor do I get angered by pronouns. I would still rather people use either 'she' 'they', but I get that it feels unnatural. And I don't get annoyed by it.
Genderfluid is someone who frequently switches between genders. This is the group that gets the most hate. People consider it as a joke. I know first hand that it's not. And anyone claiming to be genderfluid, I respect your braveness and wish you the best of luck in living your own way! Non-binary is someone who doesn't identify as a set gender. This is kinda recognisable, but since it's a small portion of people, it's still not recognisable throughout the population. So most people ignore it.
And then you have transgender. Which, in it's main definition, describes someone who's sex assigned at birth doesn't match up with their sense of personal identity. This group is the most common in the gender dysphoria category. And thus is the most accepted among people. Yes, trans people get hate, but that's just modern life I suppose.
Of course, the transgender umbrella term covers pangenders, bigenders, agenders, and many others that could be a blog post all in itself. But genderfluid and non-binary are the ones I identify with.