Buffers are used to prepare the natural nail and are more flexible than files. They consist of fine sandpaper applied to four sides of a foam block. Also, buffers aren't as rough as files, so you don't risk damaging your nails if you use them regularly for manicures or artificial nail sculpting techniques.
A nail file is used to trim, shape, polish, or trim artificial nails. False nails are best shaped with emery boards as they are gentler than metal files.