/etc/resolv.conf is a file that holds the configuration for the local resolution of domain names. Normally this file is either static or maintained by a local daemon, normally a DHCP daemon. But what happens if more than one thing wants to control the file? Say you have wired and wireless interfaces to different subnets and run a VPN or two on top of that, how do you say which one controls the file? It's also not as easy as just adding and removing the nameservers each client knows about as different clients could add the same nameservers. Enter resolvconf, the middleman between the network configuration services and /etc/resolv.conf. resolvconf itself is just a script that stores, removes and lists a full resolv.conf generated for the interface. It then calls all the helper scripts it knows about so it can configure the real /etc/resolv.conf and optionally any local nameservers other can libc.