I've seen a lot of people on here confused about what sexuality is what, so I figured I'd write a short my take explaining some of the biggest ones
1. Homosexual (Gays and Lesbians)
These are the men and women who are ONLY attracted to the same gender as them, both romantically and sexually. This is the most known of LGBT sexuality.
Bisexuals are attracted to both sexes. Some may prefer one slightly over the other, but they still are attracted to both of them. Bisexuals are NOT "Confused". They simply like both sexes.
This group is often confused with bisexuals.
The difference is this: Bisexuals like men and women, while pansexuals like ALL genders (agender, bigender, etc).
Demisexuals are ONLY attracted to those who they have formed an emotional connection with.
This is not the same as only dating someone you have known for a while. You, (unless you're demisexual), can look at a stranger and find them hot. You can look at someone you haven't known and say "wow, they're attractive". A demisexual can not experience this.
These people experience no sexual attraction at all. Some will have sex with their partners if their partner wishes, but they don't feel the need or desire for sex like others do.
(However, they CAN experience romantic attraction, which is separate)
6. Grey Asexual
This one is often missed. A grey asexual very very rarely experiences sexual attraction, or only to a very few certain people.
7. Biromantic Homosexual/Biromantic Heterosexal
A biromantic experiences ROMANTIC attraction for both sexes. Meaning they could enjoy the idea of cuddling, going on dates, or even kissing both genders. However, they only experience sexual attraction to one of these sexes. They only would enjoy sex with one of them.
I hope this described these well enough and maybe taught some people some. These are pretty basic definitions and if you want to learn more I'd suggest looking online and doing some research.
If I made a mistake in one of these descriptions, please comment and tell me too! Im obviously not all of these sexualities, so while I did my best there's always the possibility of mistake.