We'll resist the urge to say duh. These are the fairy tales upon which all subsequent fairy tales are modeled. Okay, not all, but a lot. So these are pretty conventional, happily-ever-after stories full of magic and romance and cannibalism.
About that last part: before fairy tales were sanitized in the process of becoming acceptable for children's literature, they were told by and for adults, too. So some of them have some pretty mature themes, sex and violence among them. The Grimms weeded a lot of those out, but there are still moments when we're like, Whoa! That dude totally ate his son by accident. And so on.
A few of the tales also fall under the headings of fables, parables, and folklore, legend, and mythology, because the Grimms didn't really distinguish between all those categories the way we might today. All the stories they collected kind of got lumped in together, in part because they were all distinctly different from the elite written literature of the time. Yes, this is the sort of thing that gives folklorists and archivists nightmares.