Personal wikis, as the name implies, a wiki for one person. Folks use them for different reasons. Could be used for note-taking, a non-chronological blog, shitposting, archival, or whatever other reason. Generally they're written and maintained by one person. To read about this site click here.
This style of site was a trend from the late 2000s 1), and most of these sites have died. They happen to be one of my favorite styles of site, so if you know of any quality examples not linked or mentioned here, please shoot me an email.