Polkit is a system service installed by default on many Linux distributions. It’s used by systemd, so any Linux distribution that uses systemd also uses polkit
When you try to perform an action which requires a higher level of privileges, the policy toolkit can be used to determine whether you have the requisite permissions. It is integrated with systemd and is much more configurable than the traditional sudo system. Indeed, it is sometimes referred to as the "sudo of systemd".
