Vulnerability Management is an on-going process that evaluates an network environment for potential threats (vulnerabilities), analyses those threats and ranks them into a series of priorities. Once the threats have been identified, it then become a matter of remediating the threat and removing the potential vulnerability access point into the environment.  The methodology is simple, but in a digital world with multiple applications, patches, updates there are always potential new vulnerabilities that a threat actor will try to exploit.  This is why a vulnerability management program is critical to any business environment and you will find this process in any set of industry standard security controls.