Every time a browser, an app or a server needs to reach another machine by name, DNS is the step that turns that name into an IP address. It is one of the oldest parts of the internet's plumbing, and one of the first things a support engineer should suspect when 'the internet is down' actually means 'one thing is down.'
A DNS record maps a name to a value — most commonly an A record mapping a hostname to an IPv4 address, but also MX records for mail, CNAME records that point one name at another, and TXT records used for verification and anti-spoofing policies like SPF and DKIM.
Resolution happens in stages: a resolver checks its cache, then asks a recursive resolver, which walks from root servers down through top-level domain servers to the authoritative server for that specific domain. Caching at every stage is what makes DNS fast — and what makes a changed record take time to propagate everywhere.
For anyone starting in networking or IT support, the practical skill is diagnostic: knowing how to query a record directly, tell a caching problem from a misconfigured record, and read a zone file without panicking. That diagnostic habit is exactly what our Networking Fundamentals & Troubleshooting course builds from week one.