[cesarb]

What the parent poster means is that each application does its own DNS lookup separately and independently. The family of functions you linked to, plus the newer getaddrinfo family of functions, is implemented in the C library within each process, not as a system call or as a separate daemon. These functions read the /etc/nsswitch.conf file, load the C library plugins listed there, and call each one in sequence - still within the same process. The most common setting is a variation of "hosts: files dns", which first reads /etc/hosts, then reads /etc/resolv.conf and connects directly to the DNS servers listed there, without using any system level "DNS lookup" daemon (unless you have nscd enabled).