Extract fields or charcters from strings.

cut -c 3,2,10    files (characters)
cut -f 1,3       files (fields separated by tab)
cut -f 1,3 -d' ' files (fields separated by space)
cut -f 1,3 -d':' files (fields separated by :)

cut -b   files   (bytes)
$ who
foo      console  Apr  8 18:57 
bar      ttys000  Apr  9 07:42 
moose    ttys001  Apr  8 18:57 
$ who | cut -f1 -d' '
foo
bar
moose