Picture Style parameters include contrast, hue, saturation and sharpness.
A Picture Style can also include subtle changes to a single colour, making blues lighter, or creating a more vivid red. Some Picture Style settings are aimed at specific subjects - Landscape or Portrait, for example. Others are more general - Standard, Faithful, Neutral, for example. Before you shoot it is sometimes difficult to know which Picture Style will best suit the subject. With DPP and a raw file you can delay the decision until the image is on your computer screen and then experiment.