What each record does
A/AAAA point your domain to a server; CNAME makes one name an alias of another; MX says where email is delivered; NS lists the nameservers in charge; TXT holds SPF, DMARC and verification codes; CAA limits which authorities may issue your SSL certificates.
Why results can differ
DNS answers are cached for the TTL shown. After a change, some networks may show the old value until it expires. Use the propagation checker to compare resolvers worldwide.
Frequently asked questions
If you changed it recently, cached copies may still be served until the old TTL runs out. Also check you edited DNS at the provider your NS records point to.
3600 seconds (1 hour) is a sensible default. Lower it to 300 a day before a planned change so the switch happens quickly.
No. Lookups are processed on the fly and not saved.