Blenster wrote Mon 3/9/15 @14:27 EDT:
A quick correction: transgendered does not refer to sexual orientation.  More like sexual expression, however that term is problematic due to confusions with sexuality and that sort of expression.

Transgender refers to what gender a person chooses to express themselves as (regardless of biological sex as indicated by the XX/XY chromosomes, though this is sometimes complicated in individuals who have chromosomes of both sexes or whose DNA has expressed different genetalia than their chromosones would normally be expected to).  For example someone who may have been identified at birth as a female may choose to express as a male but may find either males or females attractive for their sexual partners.  Now which of these encounters counts as "homosexual" in nature is generally down to how accepting of transgenderism a person is; personally I feel that a person who expresses as a man who is with a person who expresses as a woman is straight, and someone who presents as female and prefers to be with other women is gay.  Some people, unable to let go of how they feel "sex"/"gender" is assigned (frequently based on genealia rather than chromosomes - mostly because it's hard to test folks DNA but easy to make a judgment based on more obvious external fleshy bits) will consider a person they identify as a "woman living as a man" (rather than a simply accepting them as a man) having sex with a woman as homosexual in nature, however this is discouraged as transphobic.

Sexual orientation refers to things like straight, gay, bisexual, pansexual, asexual, etc.

Transgenderism uses different terms like cis, transgendered man, transgendered woman, trans man, trans woman, FTM, MTF, etc.

An excellent primer on this material can be found here: