When this matters
DNS matters as soon as you connect a custom domain, add a subdomain, verify a service, or route traffic for email and web hosting. It also shows up when something works on a preview URL but not on your nice public domain.
Small example
A common setup points the main domain to your hosting platform and a `www` subdomain to the same place with a CNAME.
example.com A 76.76.21.21
www.example.com CNAME cname.hosting-platform.comCommon mistake or lookout
Changing a DNS record and expecting instant results. Some updates propagate fast, others take time, and mixing up `A`, `CNAME`, and verification records can send you on a very annoying scavenger hunt.
Why this matters for vibe coders
Vibe coders often get stuck right at the finish line because the app is deployed but the domain is not pointing correctly yet. A little DNS knowledge turns “the site is broken” into “the record is wrong” much faster.