A code signing certificate is used to sign software and other code. It allows the recipient to verify that the software truly comes from you and that no one has tampered with it.
No more security warnings
The publisher of the certificate is trusted by browsers. This lets a browser know that the signee of the software has been verified. The browser will no longer issue security warnings to inform users that the publisher of the software is "Unknown".
A code signing certificate can also be used to add a timestamp. This ensures the signature remains valid even after the certificate that was used for the signing has expired. It allows you to verify that the certificate was indeed still valid at the time of signing.
The longer the validity, the higher your discount.