The SHA-256 (Secure Hash Algorithm) is one of the best cryptographic algorithm published by the National Institute of Standard and Technology used to certificate the files.
The official packages of ManuelLab are released with correspondent SHA-256 strings. These strings are used to identify and check the integrity of the packages, in order to be sure that you have downloaded a file that is not corrupted or altered in any way.
Using SHA-256 to check the file is very simple.
You have just to use an utility to calculate it and compare your result with the string published in the download page. If they are different, the package is corrupted and you have to download it again.
In most of Linux distribution, the sha256sum is part of standard distribution. Just type:
to calculate the string. In Windows there are many external utilities.