Difference between /etc/hosts and /etc/resolv.conf

/etc/resolv.conf specifies the nameservers for resolver lookups, where it will actual use the DNS protocol for resolving the hostnames.
Typically the /etc/hosts file is used for administrative purposes such as backend and internal functions, which is substantially more isolated in scope, as only the local server will reference it it./etc/nsswitch.conf specifies the lookup order with the hosts