>>3397019P is program auto. The "program" essentially picks the lowest shutter speed at which you can shoot handheld (depending on the lens you have mounted) and the aperture that will give you the largest depth of field. It does this according to a "program line" which is a hell of a lot simpler than you might expect.
You can also "shift" the program line if you don't like the shutter speed/aperture combo it picked while maintaining the same exposure. It's the best of both Aperture and Shutter priority modes, though beginner and intermediate photographers avoid it because they think it's less "pro" and gives them less control over the image. This is due purely to ego and inexperience.
