DNS (Domain Name System)
Short definition
DNS is the distributed lookup system that translates domain names into the actual IP addresses of servers online.
When a visitor types a domain into a browser, DNS works out which server that name points to and routes the connection there. It happens in a fraction of a second and stays invisible most of the time.
DNS records are not stored in one place; different record types carry different jobs. An A record points to the website, an MX record routes email, a TXT record carries verifications such as SPF.
A DNS change does not take effect instantly, it spreads across the network over what is called propagation, which can take hours. DNS is usually managed through the domain registrar or the hosting panel.
Rather than waiting and guessing, a browser-based DNS lookup tool or the dig command technical teams use can query a record directly from outside, showing exactly what the world currently sees. During a migration this is the practical way to confirm whether a change has actually propagated, instead of assuming it has and moving on.
Why it matters
Misconfigured DNS means a site will not load, email stops arriving, or traffic quietly points at an old server. During a migration or renewal, copying DNS records correctly is the only guarantee of an uninterrupted switch.
Illustrative example
A spa chain checked its DNS records before switching hosting providers, made the move at midday, and customers noticed no downtime at all.
