Each of these sets of five words has an odd member out. The other four words fall under a specific category, which can then be further generalized with a single word. Once you discover each of the five odd words out, those five words will come together to form a category of their own! Are you up to the challenge?
EDIT: I wasn't clear enough with one facet of the puzzle. The categories that each group is sorted into can be generalized into one word "super-categories", which very generally (or in some cases, specifically) describe how each group is perceived. These one word super-categories then will become their own category, at which point the puzzle should end with a pretty clear understanding of how the words were chosen.
EDIT2: To see if I can nudge this along, here's a hint:
The backbone of the puzzle is the category which can be formed by the single-word "super-categories" of the five existing categories. The number of elements in the category is an important hint that can potentially guide you towards the solution.
EDIT3: Another day, another hint!
I used the phrase "how each group is perceived" earlier when describing the one word super-categories - that terminology was very specifically on purpose. Your perception of these groups will be very important to really figuring out the crux of the puzzle.