DNS is Domain Name System, the system that maps domain names to the servers and services that handle website and email traffic.
It matters because development decisions affect speed, security, scalability, tracking, SEO, and maintenance. A site that looks good but is fragile or hard to update can quietly hold back every marketing channel.
Example
During a hosting move, a team updates the website’s DNS records to the new host while preserving the email records. Changing all records indiscriminately could interrupt email even if the new website works.