The PIR setting is the sensitivity of the 'passive infrared' sensor, usually has three settings low, normal, and high. In colder temps the PIR can detect movement farther away, sometimes past the flash range of the camera, so it's best to set this to low during the winter, high during the summer, normal in the spring and fall.
the Resolution setting is the pixel size or quality of the photo you want to take. The higher the resolution the fewer pics you will be able to get on your memory card, but it will be easier to distinguish features of the subject in the pic. If you use a 2GB card and check your camera at least once a week you want the highest resolution setting. If you plan on leaving the camera in the woods for months at a time, either get a larger memory card or lower the resolution.
the Delay setting is the amount of time you want the camera to wait after taking a pic until it takes the next pic. if the camera is looking over a bait pile or food plot you want to set the delay to about 1 minute. if the camera is looking over a trail or scrape you want to set the delay to 10 seconds or as low as it will go so you don't miss anything.
hope this helps