Low-cost storage for data that's rarely accessed but must be kept long-term. Like a storage unit in the basement - cheap to keep things, but takes time to retrieve them.
Hospitals use archive storage for old patient records that must be kept for legal reasons but are rarely accessed.
All are object-storage archive tiers/classes designed for long-term retention at very low storage cost, trading off higher retrieval latency and retrieval/early-deletion fees. AWS offers separate Glacier and Deep Archive options; Azure uses an Archive tier within Blob; GCP uses an Archive storage class; OCI provides an Archive tier.