cksum prints CRC checksum and byte counts of each file.
cksum can be used to check if files are transfered without error (or not corrupted during storage).
cksum * > cksum.list
generates checksums' file. After transfer (or after a long storage) you can check if files are the same:
cksum * cksum.list-2
diff cksum.list cksum.list-2
cksum also can be used for fast searching for duplicates. After issuing
identical files have same checksums.
Conversely, files with same chcecksums and same sizes almost always are identical. This can be checked further with diff.
These are related to summarizing the contents of files.