It acts as an intermediary between programs that supply name server information (e.g., DHCP clients) and programs that use name server information (e.g., resolvers).
In a system without resolvconf, the file is normally maintained manually or by a collection of scripts.
Resolvconf controls access to the file, allowing many programs to use it at the same time.
[1] In securely administered environments the resolvconf program (or daemon, depending on the implementation) causes uneasiness since it interferes with the containment of resolv.conf security vulnerabilities, making changes to it without authorization.
By default, resolvconf is often replaced by systemd-resolved on modern operating systems, which provides a stub resolver in addition to managing resolv.conf.