What Is DNS? DNS Records and Resolvers Explained
DNS is a distributed naming system that retrieves records associated with domain names so browsers, mail systems, and other internet services can find the information they need.
How it works
When an application needs DNS information, it asks for a specific name and record type. A recursive resolver finds or reuses an answer from the domain's authoritative DNS information, then returns that record to the application. The answer might contain an IP address, a mail server, an alias, or text used for a policy or verification step.
From a domain name to a DNS answer
A DNS question contains both a name and a record type. Looking up the A record for example.com asks for an IPv4 address, while requesting its MX record asks where mail for the domain should be delivered. A resolver can therefore return different data for the same name depending on the requested type.
For example, example.com could publish an A record whose value is 192.0.2.10. A browser can use that result when connecting over IPv4. A separate AAAA record would provide an IPv6 address, and the absence of one type does not imply that every other record or service for the domain is absent.
Resolvers commonly cache answers for the record's time to live (TTL) so they do not repeat the complete lookup for every request. That caching explains why a recently changed record may not be returned through every resolver immediately, but detailed timing and disagreement troubleshooting belong to the DNS propagation guides.
Recursive resolvers and authoritative nameservers
A recursive resolver answers applications such as browsers and mail servers. It may already have a usable cached answer; otherwise, it follows DNS referrals until it reaches the authoritative nameservers for the relevant zone. Home networks often use a resolver supplied by an ISP, while public and organization-operated resolvers are also common.
Authoritative nameservers publish the DNS information configured for a domain or delegated zone. They are the source a resolver consults for a fresh authoritative answer, but they do not normally browse websites, deliver mail, or make application connections on the user's behalf. DNS supplies records that those other services can use.
These roles are separate. Changing a record at the authoritative provider does not directly erase copies held by recursive resolvers, and changing the resolver used by a device does not edit the domain's authoritative data.
Common DNS record types
A records map a name to an IPv4 address, while AAAA records map it to an IPv6 address. A CNAME makes one name an alias of another: www.example.com CNAME example.com tells a resolver to continue with the target name rather than storing an address directly in that alias record.
MX records identify mail exchanger hostnames and their priorities. For example, example.com MX 10 mail.example.com says that mail systems should consider mail.example.com at priority 10. The mail hostname then needs address records of its own; the MX record is not itself an IP address or proof that mail delivery is working.
TXT is a general-purpose text record. It is commonly used for email policies, service verification, and other published metadata, but it does not have one universal meaning. Its interpretation depends on the protocol or service that requested the record.
Using DNS lookup results correctly
A DNS lookup shows the answer returned through the resolver and request path used for that check. It is a useful observation of a particular name and record type, not proof that every resolver worldwide currently returns the same value. Resolver cache state, intentional geographic answers, and split internal DNS can produce legitimate differences.
No record is different from a failed lookup. A domain may exist without publishing the requested record type, while a timeout or unavailable resolver means the check could not obtain a dependable answer. Also, a DNS record can be present even when the website, mail server, or other destination it names is unavailable.
Start by querying the exact hostname and record type relevant to the service. If a recent authoritative change appears inconsistent across networks, use the DNS propagation material for TTL and resolver-comparison guidance rather than repeatedly changing otherwise correct records.
Practical guidance
- Query the exact hostname and record type used by the service you are investigating.
- Treat a returned value as the queried resolver's current answer, not a worldwide-state guarantee.
- Distinguish a missing record from an unavailable lookup and from an application that is not responding.
Common question
Is DNS the same as web hosting? No. DNS publishes records that can direct a browser to a host, while web hosting serves the site's content. Either can be configured or unavailable independently.