Introduction of The Symbol P, S, A and M on Nikon D3000 SLR Cameras

P = automatic programmable

camera set shutter speed and aperture for optimal lighting. recommended for shooting and in other situations where there is no time to set the camera

S = automatic shutter priority

users choose the shutter speed, camera selecting aperture for best results. used to freeze or blur motion.

A = aperture priority auto

the user selects the aperture; camera choose the shutter speed for best results. used to blur the background and focus to the foreground and background at the same time

M = Manual

users can control shutter speed and aperture. set the shutter speed to "bulb" (custom shutter speed) or "time" for a long time lighting

100 Digital SLRs here
Nikon D3000 10.2MP Digital SLR Camera with 18-55mm f/3.5-5.6G AF-S DX VR Nikkor Zoom Lens
Nikon D3100 14.2MP Digital SLR Camera with 18-55mm f/3.5-5.6 AF-S DX VR Nikkor Zoom Lens
Nikon 55-200mm f/4-5.6G ED IF AF-S DX VR [Vibration Reduction] Nikkor Zoom Lens