Here is a definition of a transgender person from simple searching,
Gender dysphoria is the material condition that drives the transgender idea. What we know of is the difference is that a tomboy is not by any means a "trans man" because she is comfortable by being a little masculine while retaining a female body. That is because it would be preposterous to reduce the notion of transgender as being something that dresses and behaves as an opposite gender for fun.
What trans people are is not the same as what tomboys and femboys are. Sure, both of them may have gender dysphoria but the difference is that trans people actually want to be the desired gender unlike tomboys and femboys who just want to dress differently and not really care about if they wanna be full-on biological men or women. Hence, the campaign for a full, free, and satisfying affirming care for trans people which is also free but fair and just is what we need to give emancipation of trans people from their gender dysphoria that they're suffering from.