Recap: Names

A name has to become an address before anything connects, and two things can answer the question.

Your machine checks /etc/hosts first. Whatever it finds there wins outright, and DNS is never asked. Only if the name is absent does it go out to a DNS resolver, which usually replies from a cache, hence the familiar non-authoritative label.

cat /etc/hosts        # checked first, and it wins
nslookup example.com  # ask DNS when the file has nothing

Records come in types, A and AAAA for addresses, CNAME for an alias, MX for mail, TXT for free text, and each carries a TTL that decides how long it may be cached.

The habit worth keeping: resolving and connecting are two separate steps, and knowing which one failed is most of the diagnosis.