Nikon D3300 - Manual (Page 121)

101 P, S, A, and M Modes
A Shutter Speed and Aperture
Shutter speed and aperture are shown in the viewfinder and
information display.
Shutter speed
Aperture
Fast shutter speeds ( 1 /
1600
s in this
example) freeze motion.
Slow shutter speeds (here 1 s) blur
motion.
Large apertures (such as f/5.6;
remember, the lower the f-number,
the larger the aperture) blur details
in front of and behind the main
subject.
Small apertures (f/22 in this case)
bring both background and
foreground into focus.