Includes themes/actions/depictions of things like: spanking, sex toys, bdsm, bondage (any kind of restraints keeping you bound/in place), rope play, wax play, marking/biting (not regular hickeys, rather the dom is insistent on marking their sub as theirs), whipping, exhibitionism, role-playing, kinks, masochism/sadism, submissive-dominant relationships, degrading, erotic asphyxiation, flogging, CNC, etc. Nothing too extreme (as in actual assault, actual rape (obvious, non-dubious rape).
Most of the stories her are maledom works, but there are some femdom works on this list as well (I know a lot of people like those, but I don't; I'm only including those that at least have a plot that I like. Other than that, it's mainly maledom stories). Then, there are some stories whose "main theme" isn't smut, but have some smut/sex scenes in it, where there are some fetish/bdsm-elements (for example: Elixir of the Sun has some sex scenes like that in it, but that story isn't about sex).