It associates domain names with typed data in resource records. Address records help applications locate services, but DNS also publishes mail-routing, delegation, service, verification, and other information; it is not simply an internet phone book.
A client normally asks a recursive resolver for a name and record type. The resolver may answer from cache or follow delegations through the DNS hierarchy to authoritative servers, then cache the result according to its time to live. The global DNS uses the public root; private DNS uses a different naming context.
Key points
Distributed authorityAdministrators control zones, and delegations connect them to the hierarchy without placing all data in one database.
Typed recordsA, AAAA, MX, NS, CNAME, TXT, and other record types have different purposes; one name can have multiple records.
Resolver roleRecursive resolvers perform resolution for clients, while authoritative servers publish data for zones; either may loosely be called a DNS server.
Important limitationA DNS response tells a client what the consulted DNS system returned. By itself, it does not prove that the destination is safe, authenticate unsigned data, encrypt the query path, or guarantee that cached information is current beyond its defined caching rules.