What this DNS lookup queries
The tool asks public recursive resolvers for the record types that matter in day-to-day operations: A and AAAA for IPv4 and IPv6 addresses, NS for the authoritative nameservers, MX for mail routing, TXT for SPF, domain verification and similar data, CAA for certificate authority restrictions, SOA for zone metadata and CNAME for aliases.
Each answer is shown with its TTL and the resolver that returned it. If a record type does not exist, the result says so explicitly, because the absence of a record is often the answer you were looking for.
Record types in plain language
A and AAAA records map a name to addresses. A CNAME says that a name is an alias for another name; it cannot coexist with other records at the same name, which is why a bare domain cannot normally be a CNAME and providers offer ALIAS or flattening features instead. NS records list the servers that are authoritative for the zone. MX records list mail servers with a preference number, where the lowest number is tried first.
TXT records hold free-form text, used today mostly for SPF policies and ownership verification tokens. CAA records name the certificate authorities allowed to issue certificates for the domain. The SOA record carries the zone serial number and timers, including the value that controls how long a nonexistent answer is cached.
TTL, caching and the propagation myth
DNS changes do not spread across the internet like a wave. When you change a record, your authoritative servers start returning the new value almost immediately. What takes time is that resolvers around the world have cached the old answer and are allowed to keep it until its TTL runs out. A record with a TTL of 3600 can be served from cache for up to an hour after you change it; one with a TTL of 300 for five minutes.
This is why a percentage figure for propagation is not meaningful: there is no fixed population of servers to count, only caches that expire at different moments. The useful questions are what the authoritative servers return now, what the old TTL was and how long ago the change was made. Negative answers are cached too, for a period derived from the SOA record, which explains why a brand new record can appear missing for a while to a resolver that looked it up just before it existed.
Not a copy of the zone file
A DNS lookup asks specific questions about specific names. It does not list every record in a zone and cannot discover subdomains you did not ask about. Full zone transfers are disabled for outsiders on practically every properly run nameserver. To check a subdomain such as mail.example.com or a service record such as _dmarc.example.com, query that name directly.
Answers can also legitimately differ by location. CDNs and managed DNS providers return different addresses depending on where the query comes from. Two tools showing different A records for the same name are not necessarily in conflict.
Common problems a DNS lookup reveals
Typical findings include NS records in the zone that do not match the delegation at the registry, MX records pointing to a hostname that has no address or to a CNAME, more than one SPF record in TXT, a forgotten AAAA record pointing at an old server while the A record was updated, CAA records that block the certificate authority you are trying to use, and very long TTLs on records you are about to migrate.