Please let us know how to find comparison between two files. The files have same file contents.
if there are any differences in the file the output should show up the actual difference in both the files.

You can use the diff command. There are also graphical frontends to this command e.g. kdiff3.

For sorted files of single items, you can use the "comm" command as well. I will use it at work using Cygwin to compare inventory list from video devices. It is one of the core-utils so you should have it. You could of course use: "comm <(sort file1) <(sort file2)". In the output: Column 1 contains files unique to file1, Column 2 contains items uniq to file2 and Column 3 contains items common to both. You can suppress any column by including the column number as an option:
comm -23 <(sort file1) <(sort file2)
will print the items unique to file1. The other columns 2 & 3 are suppressed.

If you have two lists and need to verify that the items in list1 aren't in list2, you could use "grep -f file1 file2".

Refer to the manpages for comm and grep for all the options.