I'll answer with Tym J. Misery's Famous Sexuality Guide;
Sexual orientation: The term sexual orientation is generally used to describe how a person — if they do — finds themselves sexually, affectionally, and/or romantically attracted to other people in regards to the gender of those people; which gender or genders of person a given person can be in love with and wants to have any kind of sex with. There may be varying degrees of those things or experiences of those things being more separate than unified: for instance, a person may be very sexually attracted to men, but more emotionally attracted to women or someone may find that romantic attraction for them, to anyone, usually plays a bigger part than sexual attraction.
Heterosexual (or straight): Someone who is solely or primarily (mostly) attracted to people of a different sex or gender than them, such as men who are attracted to women.
Queer: Generally, queer is an umbrella term that describes a person who is not heterosexual. Someone may use the term queer as the way they identify, period, or may use terms like those below and also identify as queer.
Homosexual (or gay, lesbian, same-gender loving, MSM or WSW): Someone who is solely or primarily (mostly) attracted to people of the same or similar sex or gender as them, such as men who are attracted to men.
Bisexual: Someone who finds they can feel attraction to people of more than one gender, be that to both men and women, to people of all gender identities, or who doesn’t experience gender as a major factor in their attractions, period.
Pansexual or Omnisexual: Someone who can feel attraction to people of all gender identities, or who doesn’t experience gender as a major factor in their attractions, period.
Asexual (or nonsexual): Someone who has not experienced or does not experience sexual attraction to others or does not have a desire to be sexual with partners. In other words, someone who is not sexually attracted to anyone of any gender.
Apasexual: Someone who feels a lack of significant interest in sex, or feels apathetic about sex in general.
Androsexual, gynesexual, ambisexual or skoliosexual: These terms are a different framework for orientation than the framework of heterosexuality, homosexuality and bisexuality, one that can be more inclusive and expansive than hetero/homo/bi and doesn’t require the gender of the person who is feeling the attraction to be defined in a given way, or at all. Androsexuality refers to someone who is attracted to masculinity, gynesexuality to femininity; am ambisexual is someone who can be attracted to both or either, or experiences gender as a non-issue, and a skolisexual, someone who is attracted to non-cisgender or non-binary people in general. Asexuality is also included in this framework. This framework doesn’t make rigid asssumptions about the other person’s gender, either: a person can be attracted to masculinity in women or femininity in men, for example.
Pomosexual: Someone who rejects or does not identify as or with any categorization of sexual orientation as a form of identity. Pomosexual is basically a term for someone who is of the “labels are for soup cans” camp regarding orientation.
Questioning (or -curious or -flexible, like bicurious or heteroflexible): Someone who isn’t sure right now, or has never been, of what their sexual orientation is; who is in the process of figuring that out. Terms like bicurious or whatever-flexible usually are used by someone who feels an interest or curiosity about a given gender of people sexually, but is still in the process of questioning. A term like that is sometimes also used to describe an interest in people of a given gender that’s there, but not felt as so central to be part of someone’s overall orientation.