Heterosexual aka "Straight"
Heterosexuality is romantic attraction, sexual attraction or sexual behavior between persons of the opposite sex or gender.
Homosexuality describes romantic or sexual feelings or behaviour between members of the same sex or gender.
Asexuality is a lack of or low sexual attraction. Generally it does not imply a lack of romantic feelings, although the term is an umbrella term that can cover a range of asexual sub-identities.
Bisexual aka "Bi", "Goes both ways", "Sitting on the fence", "AC/DC"
Bi-Alliance uses the term "bisexual" to refer to someone who experiences attraction (one or more of the following kinds: sexual, romantic, emotional, or affection) to more than one gender.
Pansexual aka "omnisexuality", "gender blind"
Pansexuality describes sexual or romantic attraction towards people regardless of their sex or gender identity. Pansexuals find gender and sex irrelevant in determining whether they are attracted to others.
There is debate regarding whether bisexuality excludes complex or non-binary genders or whether the word is implicitly inclusive. The word "pansexual" is explicitly inclusive, which some people prefer.
Demisexual aka semisexual, asexual-ish, sexual-ish
Demisexuality is a sexual orientation in which someone feels sexual attraction only to people with whom they have an emotional bond. Most demisexuals feel sexual attraction rarely compared to the general population, and some have little to no interest in sexual activity.