The P4 pro gives you the opportunity to shoot aperture priority (A) or shutter priority (S).
You get to decide what is more important to control for the shot you want, aperture or shutter speed.
If you were night shooting and wanted a two second shutter speed to show light trails, you would choose shutter priority, set your shutter speed to 2 seconds and let the camera choose an appropriate aperture.
If you wanted all your shots to be taken at the same aperture, you could choose aperture priority, select the desired aperture value and let the camera choose a shutter speed.
Of course there is another parameter, the sensitivity (ISO) which you can lock down or let the camera choose.
For your average daylight scenes, choosing settings won't be too critical as there will be enough light to avoid anything tricky.
It's when you get down to low light situations where the settings you choose would be more important.
If you aren't sure what you are doing and set the aperture at f 5.6 (Aperture priority - A) and let the camera handle the ISO and shutter speed, you'll get pretty good results in almost all daylight situations.