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 low-cost object storage options for long-term retention with higher retrieval latency and (often) retrieval fees. AWS uses dedicated Glacier classes within S3, Azure uses an Archive tier within Blob, GCP uses an Archive storage class, and OCI offers an Archive tier in Object Storage.