The MD5 Message-Digest Algorithm is a widely used cryptographic hash function with a 128-bit (16-byte) hash value. Specified in RFC 1321, MD5 has been employed in a wide variety of security applications, and is also commonly used to check data integrity.
As mentioned above MD5 CHECKSUM is used to check the integrity of the file. If you think the legal file that you have downloaded from products official website has been modified or if you want to check whether you have downloaded the exact file provided by the product owner you can use MD5 checksum.
MD5 Checksum algorithm will generate a group of character strings using which we have to match and verify the checksum of downloaded file and File in the site.
Use the following command in Terminal to verify checksum of the file:
$ md5sum filename.extension
spv@Pras_linux:~/Downloads$ md5sum mongodb.pdf ec70cfc19d9babff02484a74e22ebbbc mongodb.pdf
In the above 1st line is used to generate the md5sum of a pdf file and the 2nd line is the output of the command.
Now in order to verify whether data integrity is maintained properly you need to check the md5checksum of the pdf file in its official site, provided they have included it.
All the OpenSource Products , when released will have md5checksum string in their official site. This ensures you are using a right product provided by the original developer.