The second bullet point is "There are two genders."
In the vernacular, people may use gender and sex (in the sense of whether an entity is male or female) interchangeably, but in scientific language they do not mean the same thing. Sex is a biological term, gender a sociological term.* Biologically, most metazoans mostly come in two sexes, designated male and female, distinguished by their role in reproduction. They both contribute half the genetic material to offspring, but the gamete -- the cell that combines the genes of the two parents and then divides and redivides to produce the new animal -- remains with the female and receives nutrition from it during its initial development. Some species can reproduce asexually, and some (notably some annelids) are hermaphroditic, meaning they have the requisite organs to play both the male and female role in reproduction. The genetic mechanism that distinguishes between males and females differs among phyla.
We all know that humans exclusively reproduce sexually, the occasional religious myth aside. However, not everyone is born definitively male or female. Most of the time people who have two X chromosomes are definitively female, and people with an X and a Y are male, but not always. Some people are born with ambiguous genitalia.
Most people have an inherent desire to engage in sexual activity -- another meaning of the word sex -- which evolution obviously favors since it's essential to reproduction. However, we have a lot of inherent desires that get put to uses other than the ones that drove their evolution. People don't just run after prey, they do it for fun and competition. We don't just use our hands to make tools, we don't just talk to collaborate on tasks. I could go on and on. Part of the behavioral reward for reproductive sex comes from rubbing the genitals together, and we can rub them against some other body part or some other object entirely and get a similar effect. Which as you know people do quite often. (Our close relatives, bonobos, engage in sexual activity with each other quite indiscriminately, regardless of their biological sex, age or familial relationship, as a means of social bonding.) So sex has other functions than just reproduction.
Sexuality refers to the kinds of sexual activity a person prefers, and most often specifically to the preferred sex of partners. Some people just happen to want to engage in sexual activity with people of the same sex as themselves, either exclusively or some of the time. They're a minority, but they have always and everywhere existed. Actually in ancient Greece, a culture we much admire, it was a normal practice for men to engage in sex with adolescent boys. The Torah most certainly condemns homosexual activity (although you have to wonder about David and Jonathan), but Jesus never mentions it. The Torah also promulgates dozens of laws that Christians ignore. While you're denouncing homosexuals, you're probably wearing garments made of blended fabrics, eating pork and shellfish, cutting your forelocks, and failing to perform the required sacrifices.
We don't know why some people have same-sex orientation, but it seems to be hard wired early in life. Probably, people are born that way. It isn't a choice, and trying to change it doesn't work, it just makes people miserable. It doesn't do you or anybody else any harm, so why the hell should you care?
Gender refers to the social categories to which male and female humans are normally assigned. For example, until 1920, in the United States, women could not vote or hold elective office. To this day, a woman has never been elected president, and we still have disproportionately few female governors, or members of congress. On the other hand, the medical profession used to be almost exclusively male, but now half of medical school graduates are women. Obviously, gender role norms vary enormously among cultures and subcultures, and they can change over time.
But must there be just two? Certainly not, many societies including Native Americans of the plains, and Indians of Asia, have had third genders. We don't have a generally accepted non-binary category but many people feel they don't belong to the male or female category. Other people were designated as one or the other at birth, and have the corresponding sexual organs, but feel that they belong to the other category. Again, we don't know why, but it's not a choice and it isn't learned, it's something people usually recognize about themselves when they are quite young. Again, this has always been true, but people with these feelings have usually had to hide them. There is more than one example of a soldier or prominent man who was discovered to be biologically female, often only after death. And once again, it doesn't do you or anybody else any harm, so why should you care?
The tactic of Republicans to suddenly try to gin up a moral panic about transgender people is evil. It hurts people, and there is just no reason for it. None at all. It's disgusting. Agreed, there are some reasonable questions to be debated regarding athletic competition, but it seems to me we can leave that up to the respective sporting authorities. Other than that, it's no business at all of any politician and shouldn't be a concern of voters either.
*It's also a linguistic term. Many languages assign a "gender" to every noun, of which there may well be more than two. But that's really a separate discussion.