What is a Picture Style and how to create your own
The one-sentence definition
A Picture Style is the development recipe your Canon applies when generating the image: it defines sharpness, contrast, saturation and color tone, and in PF3 files also an RGB tone curve and color-range grading. The camera applies it to the JPEG, the preview and the RAW pre-render; the RAW keeps all the information and the style can be changed later in Digital Photo Professional.
The factory styles
Every Canon ships Standard, Portrait, Landscape, Faithful, Neutral and Monochrome. Standard gives the typical Canon catalog contrast and saturation; Neutral and Faithful are the preferred base for later grading because they deviate little; Monochrome applies the black-and-white conversion with optional contrast filters. The three User Def. slots are free slots where custom styles are registered (catalog PF3s land there).
What each parameter controls
Sharpness (0-7) adjusts JPEG detail enhancement; the fine settings (fineness and threshold) define at what scale and sensitivity it applies. Contrast (−4 to +4) opens or closes the global curve. Saturation (−4 to +4) raises or lowers color intensity. Color tone (−4 to +4) shifts skin between reddish (−) and yellow (+). Those four are the classic sliders; the interesting part is the advanced layer.
The advanced layer: tone curve and six-axis
The RGB tone curve remaps shadows, mids and highlights: it is the tool that defines "film contrast" (lifted blacks, soft roll-off). Six-axis grading splits the color wheel into six bands (red, yellow, green, cyan, blue, magenta) and lets you shift each band's hue, saturation and luminance: like a color wheels panel in an editor, but inside the style file and running in-camera. Curve + six-axis can rebuild the character of most analog films.
How to create your own
The canonical route is Canon's Picture Style Editor: you open a photo, move curve and color with reference points and save the .PF3. The fast route is the FilmTone web editor: start from scratch, from a catalog film, or import a .cube and convert it to a native recipe; the preview uses the same color transformation written into the file, and you download a PF3 ready to load (see the installation guide). You can also download any catalog film and adjust the name the camera will show.