There's two different common types of dysphoria... social gender dysphoria and body gender dysphoria.
Social gender dysphoria is basically being frustrated with being socially seen as your birth sex, and all of the connotations that come with it, and desire to be treated as the opposite sex is treated instead. If you have social gender dysphoria, odds are that you are envious of how guys are treated, feel like you should be treated like guys are treated socially, want to be socially allowed to do masculine things, wear "masculine" clothes, you might feel like your natural emotions and reactions to things are more like guys' are, and you're probably rolling your eyes constantly at the ways that other girls act, and the way that you're therefore expected to act because of socially being female, while looking at how guys act and feeling like that's how you should act and be expected to act.
For me, this "social dysphoria" was most manifested when people expected me to be a tough stoic "act like a man" dudebro, and people automatically gave me the "personal bubble" treatment guys get where they kept their emotional distance because I was male, and I really felt like that was wrong, to the point of grief... It actually hurt me that I wasn't "allowed" to be emotional, allowed to cry, wasn't able to do cute things, and wasn't by default be seen as someone who was nice, friendly, open, emotional. Basically, every time people treated me like a guy, it felt wrong, I felt like I should be being treated like a girl instead.
Now, understand, some people have this, but do not have body dysphoria. There are many people, transmasculine people especially, who are totally fine with escaping the typical female role by adopting a more masculine presentation, but do not need to go on testosterone or alter their bodies in order to be happy.
So with that said, here is body dysphoria. Body dysphoria is actually a feeling that your body should be that of the opposite sex, and is usually accompanied by a desire to be rid of the secondary sexual characteristics of your birth sex. It has nothing to do with social dysphoria. It's not about how other people treat you due to your body, it's about how YOU feel about your body. If you have body dysphoria, odds are that you feel like you shouldn't have breasts, or shouldn't have feminine hips and thigh fat. You'd likely be envious of masculine bodies... the muscles, the square frame, the deep voice, the more angular face, the body and facial hair, and also possibly their genitals. A lot of trans guys report feeling "phantom penises" where it actually feels wrong that they don't have one.
For me, body dysphoria manifested itself mostly through an absolute hatred of my body. I felt trapped. I felt like I was stuck in a body that was, every single year, getting more and more masculine, more and more ugly to my own eyes and mind, and less and less like the round smooth "cute" feminine body that I felt like I should have. It felt so unfair... why didn't I have hips? Why didn't I have a curvy waist? Why did I have to have all of this disgusting body hair sprouting everywhere? Why did my voice have to change? Why did my face have to keep getting squarer and squarer every year, and less and less cute and round? I hated that I couldn't seem to cry at things, felt irrationally angry a lot, and had to put up with a testosterone-fueled male sex-drive that dominated my thoughts and always felt wrong. And I actually did experience "phantom vagina" feelings where more or less every single time I felt a penis in my shorts, it actually felt to my mind like it shouldn't be there. Basically, it caused me active discomfort to live in my own body.
Those are the two dysphorias. They're by no means the be all and end all of being trans, and this is just my own experience with it, but hopefully it's at least something to think about. If you're interested, here's the official DSM diagnostic criteria for having gender dysphoria... this is the guide that a psychologist or gender therapist would use to diagnose someone as transgender:
Quote from: ___ on October 13, 2014, 02:05:33 PM
Gender Dysphoria: "A marked incongruence between one's experienced/expressed gender, and assigned gender... of at least 6 months duration, and manifested by 2 or more of the following indicators:"
1. Incongruence between one's experienced/expressed gender, and one's actual primary/secondary sexual characteristics. (Body dysphoria)
2. A strong desire to be rid of one's primary/secondary sexual characteristics due to this incongruence. (Or in young adolescents a desire to prevent the development of anticipated secondary sexual characteristics.)
3. A strong desire for the primary/secondary sexual characteristics of the other gender.
4. A strong desire to be the other gender. (Or some alternative gender different from one's assigned gender.)
5. A strong desire to be treated as the other gender. (Or some alternative gender different from one's assigned gender.)
6. A strong conviction that one has the typical feelings and reactions of the other gender. (Or some alternative gender different from one's assigned gender.)