That's gender expression. Gender identity is the internal feelings that are deep down, known for sure only by the individual, and are extremely difficult to quantify beyond "I just know."
Think of it like inner woo. The man next to you on the train may be wearing the three piece pin stripe suit and carrying a brief case, but those markers are all about expression, and inside, his identity may actually be a shy, yielding transgirl.
If I could be arsed to link them, there are a number of videos on YouTube that go into this distinction in incredibly tedious detail, and I guarantee you will be no clearer by the end of watching them. But there will probably be fairy lights on screen, and they usually have quirky three second theme tunes played on ukeleles.