Glad to see the desire to share knowledge is raging strongly today among the denizens of the SDMB.
I have mostly heard the term “sex partner” used in the medical sense of, “a person with whom you have had sex”, so that STDs can be reported to them.
I am not aware of it having any non-literal meaning.
N/A. See previous.
General through social activities. During the activity, they’ll notice someone to whom they are attracted, chat them up, ask them (or be asked) out on a date, date (which can lead to sex), and perhaps marry (which also can lead to sex).
One would expect that it takes the same amount of time for both participants…? I don’t understand the question.
Depends on the person. But my guess would be that for most initial cases, no explicit question is asked. Rather, the dominant partner gets progressively more physical as the evening continues and if the recipient of all of the attention seems happy with what is happening, then this will continue to build up to sex.
Depends on the person and their relationship with their partner.
Since it’s a technical term, encompassing all people who have sex, it’s likely that a large percentage are married couples.
Either/or, depending on context.
See first answer.
Not that I am aware of. It’s a generic label, like saying “partner” for someone that someone is dating, instead of saying “boyfriend” or “girlfriend”. “Partner” allows you to gloss over what the genders of the people in the relationship are and simply specify what the relationship is. “Sex partner” allows you to ignore the relationship (marriage, dating, swinging, etc.) and simply specify that sex has occurred since, in a medical setting, really that’s all that they care about.