A style profile contains any settings regarding print quality. These involve settings not pertaining to the machine, but settings commonly found in slicers such as materials, infill, layer height, supports, etc. Style profiles can be thought of as slicer settings, and will also allow you to control transition settings for Palette.
A printer profile can have multiple style profiles. For example, you can have a printer profile with style profiles for fine printing (0.1mm layer height) and a style profile for draft printing (0.3mm layer height).