Examples:
  comm -12 file1 file2  Print only lines present in both file1 and file2.
  comm -3  file1 file2  Print lines in file1 not in file2, and vice versa.

comm -3 prints lines that are unique to both file1 and file2 in separate
columns.
comm *-23* prints the lines that are in file1 and not in file2.

I hope the correction will be made soon enough.

Regards,
Bhargav.