If you think of the Domain name system (DNS) as a distributed Key-value store, then the domain name is half of a key. The other half of the key is the DNS resource record (RR) type. The two of these together correspond to a value for which there is an authoritative DNS nameserver.
The above is only a loose analogy, as DNS nameservers are free to assign values dynamically based on whatever they like:
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Content Delivery Network (CDN)s use geographic information about the requester (and/or redirection to their own caches).
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“Layer 7” load balancers (basically just fancy DNS nameservers) use a user-specified algorithm to divide up traffic across multiple target IPs.