short attention span huh? short answer sex magick uses the energy raised during the act. there's also a Wiccan ritual called The Great Rite, but that's commonly symbolic today.
sex magick isn't an excuse to have lots of sex, nor is it a way to have orgies. it is usually preformed by two people who are also dating/married. rarely it's two spell users who have a mutual agreement, but i've never heard of an instance where more than two people had sex and it was for magick/ritual reasons. [though it might of happened] you need to stay more focused on the spellwork than the act in most cases. [though i've never tried it so i'm no expert, i have read a couple articles on the subject] if you do decide to work sex magick, make sure you and your parter are tested regularly, and use protection to be safe. [unless you're trying to conceive but you should still get tested for any STI/STD]