Level 1 :

Sex is biological. We have males and females (dicks versus tits). But when, in a society, we refer to male and female, we very seldom refer to that. We define men and women in accordance to many non-biological traits : voice (pitch but more importantly tone), physical attitudes (the way you move, walk, sit), and even activities, emotional attitudes, and all that. You can see this in expressions like "a real man" or "a real woman" : if you are not "a real man", or not as much a "real man" as this "real man over there", it's not because you lack a biological element that makes you less male, it's because you conform less to a whole array of behavioural elements that are attached to the idea of "male". When something is "manly" or "womanly", it's not because it defines you biologically (that is helps determining your biological sex - whether you have testicles or ovaries), it's because it defines you socially. You can be "more or less of a (real) man", socially, but not biologically. How come how come ? That is because of a mix-up on words. All these things don't refer to sex, but to gender. Gender is the social equivalent of sex. It's how societies define male/female beyond biology. It's how you sort all kind of attitudes into manly/womanly, male/female (yin and yang somewhat).

Making this distinction between gender and sex is very important, because their common sense liguistic confusion is dangerous. The confusion of sex and gender (the taking of gender too seriously) leads to high normative pressure, as it serves to define as "counter-natural" any transgression to it. That is : when a biological man or woman don't conform to whatever trait is being gendered in their society, they face the argument that they are transgressing some "natural order", or that they are "freaks". This can range from tastes (activities or interests that are deemed "wrong" for one sex) to, of course, homosexuality (liking one sex rather than the other is highly gendered) and various behaviours that are oh so highly disturbing to behold because they clash with the gender/sex expectations ("effeminate" male behaviour, "tomboyish" females). And of course there is the question of feminism, where social roles are abilities are attributed to "natural functions", which are just gendered elements confused with biological determinism ("a woman? doing maths? hah!"). Plus, political rhetorics can play with that a lot, when refering to virility and questioning the testicles of, for instance, those who contest a specific conflict, etc...

None of this is extraordinarily revolutionary, as (I suppose) every one knows that when a man is considered "not manly enough", it is seldom a questioning of him having a penis. But the confusion is often strong enough in popular discourses for people to not escape this essentialisation (ie. saying that some trait is related to the unescapable "essence" of this category), and using different words keep things clearer. Also, it was necessary when, in cultural anthropology, you were forced to observe and relate the empirical reality of the relativity of gender categories : some human cultures sorting people into more than just two genders, or, more simply, "gendering" differently the behavioural traits, attitudes, etc, of people. Even observing our own societies through different epochs shows that the content of "genders" (as the social interpretation of what a "man" and what a "woman" are supposed to be) has varied a huge lot. Again, genders are very relative. They are the social constructions that one society builds around sex, at one time, in one region. And thus, they are negociable and contestable (yet generally enforced by a given society's norm and collective representation, and so deeply assimilated by its members, to the point where questionning them or being confronted to alternatives is a bewildering shock).

Level 2:

All the above treated biological sex as the simple binary ground upon which gender is extrapoated, and to which different gendered traits, values, activities, etc, are attributed. Well, things are actually a bit more complex here. Because biological sex is not clear cut either when you look at the details. And as our culture functions on two social genders, biological sex is "thought" through these dual categories. Means that all the minoritary inbetween situations (for instance "intersex") are forced into one or the other of these social genders, to the point of surgical operations at birth. We build social realities in accordance to our perception of nature, but then we also bend nature to fit our social realities. And there again, you can see that our words and concepts mislead us, and blind us to some realities. It is a circular process, related to how, generally, societies construct their realities.

So, these both levels help us understand what is going on, in reality, on earth, when it comes to real people, empirically, on the subject of sex and gender. It goes against "common sense" (the local specific "common sense" of our society in particular), and shocks a lot of people who are so used to traditional views that they react with horror to anything that challenges them. But it's a field of study that, like all sciences, helps us to grasp the world better, and it has, ultimately, the social/political consequence of helping humans to understand each others better instead of enying each others existences, or forcing each others to hide in order to not be treated as "abominations" (here I use "abomination" in the sense of something not fitting in the pre-defined mental categories that we use to sort the world - an impurity). The more refined our vision gets, the more precisely we can describe the world an communicate, the most fair and inclusive we can make society. But it's a tough work, because when you start to actually observe people's sexual identities throughout societies and over the world, the basic "male/female" categories you've learnt as a child are just shattered into a million of crazy existing personal realities. And yes, they have to be taken in account.

And no, no matter what the bible says, it is not about the study of evil. :-/
You're just saying that a majority needs no specific word apart from "the default ones" because they are the majority.

So this is a perfectly valid comparison. Words such as "locales", "natives", "autochtons" should be suppressed from your dictionary.