There's a wide spectrum of gender identity between those who identify with the gender they were assigned at birth (CIS) and those who identify with the opposite gender (transgender). On the way there we get many variations including the transvestite who feels a need to dress as a woman, and the sissy, a male who displays a tendency toward being feminine and being treated as a woman but is not transgender, although may eventually move to being fully trans.
That brings me to this site dedicated to pics of sissies and sissification. Called SissyMeme you can explore a range of different categories covering this subject. From cuckolding where the sissy is humiliated by being forced to wear a cock cage while his wife is pleasured by the cuck, to breeding - every sissy boy's dream to have a man fill them with his semen.
There's no real telling what can turn each one of us on, human sexuality must be one of the most complex and mysterious subjects to understand. There are men who are attracted to sissies just as there are men who are attracted to being one. It's not a subject that is covered in porn all that well so it's nice to find a whole site dedicated to this sexual phenomenon.
If these thoughts turn you on, or even if you're just curious about what makes someone want to be treated that way then head on over and take a look through the pics in each topic.