Immediately after birth, we are assigned with a certain sex, either male or female. In some cases people are born with sex characteristics (including genitals, gonads and chromosomes patterns) that do not fit typical binary notions of male or female bodies. These people are called intersex. Intersex is a general term that merges a wide range of variations that occur in nature. According to experts intersex people account for 0.05 up to 1.7% of the population.
In addition to the biological sex, we have gender, which is a social and cultural construct. This term has many definitions depending on the author's or scientist’s stance. The most typical definition: "sex is a social gender". What does this mean, simply? It is a set of characteristics by which we can determine who a man and a woman are, what they are like, what they look like, what they do, etc..
If we are to describe a woman by paying attention to her dress, heels, soft-spoken voice, feminine figure or long hair, we have illustrated and paid attention to her gender characteristics.
Moreover, each of us has a certain gender identity. Gender identity stands for one's attribution of self to a certain group that shares some similarities on the basis of gender. When a person's gender identity does not match the gender assigned at birth, this person is called transgender. If it matches, then the person is cisgender.
Regardless of these characteristics, a person might have different sexual orientations.Sexual orientation is usually understood as a more or less constant emotional, romantic and sexual attraction to people of a certain sex or gender. There are three common sexual orientations: heterosexual, homosexual and bisexual. Some distinguish the asexual orientation, when the attraction is absent or almost absent, as well as any interest in a sexual intercourse. Another type of sexual orientation, pansexuality, has been spoken about more often recently. It is characterized by emotional, romantic, or sexual attraction to people regardless of their gender identity or biological sex. Here lies the difference between pansexuality and hetero-, homo-, or bisexuality for which the sex of the person one is attracted to matters.
A trans* identity is sometimes confused with sexual orientation. Sexual orientation and gender identity are different things, thus, transgender people can be heterosexual, homosexual, or bisexual. Basically, just like cisgender people.
In fact, transgender people can be heterosexual, bisexual, asexual, just like cisgender people.