Code signing certificates allow software publishers to digitally sign their code, including applications, executables, scripts, and programs, to confirm that the software has not been tampered with by any outside source. This is especially important for those who distribute through third-party download sites, over which they may have no control.
Major operating systems like Microsoft Windows will show end users an error or warning message if the software they are downloading or installing does not have an encrypted digital signature, verified by a trusted Certificate Authority (CA).