diff is a command line utility that compares two sources (usually files) and displays the differences. In CS courses context, diff is often used to compare the output the student program with the output of the school solution, both provided with the same input, for debugging purposes.
Using md5sum as a diff replacement
md5sum is a common shell utility that gives the md5-hash of a file. Skipping some interesting details, files with the same hash code are completely identical. Since comparing large files stored in different computers is slightly impractical due to the time needed to transfer the files, md5sum is often used to create a md5-hash of a file in each computer, than comparing them. This technique