What does a Resource represent in OpenTelemetry, and how does it differ from span attributes?

Why this is the answer

A Resource is an immutable set of attributes describing the producer of telemetry — service.name, service.version, host.name, k8s.pod.name — attached once to every signal the process emits, while span attributes describe one operation and change per span. It is not the storage backend (that is an exporter target, not a data-model concept), not a hardware profile (host attributes are only one possible part of a Resource), and nothing to do with sampled spans in memory (that is the batch processor's queue).