Gender identity is different from sexual orientation. Gender identity is a person’s internal knowledge of their gender – the deep knowledge that they are a man, a woman, or non-binary.
Sexual orientation is about who you’re attracted to. Regardless of being trans or cis, anyone can be attracted to lots of different people. For example, a transgender man (someone who lives as a man today) may be attracted to other men and identify as a gay man. He may be attracted to women and identify as a straight man. He may be attracted to both men and women and identify as a bi man or a queer man.
For more information on transgender people and the trans movement, check out the National Center for Transgender Equality.