AWS long-term archival storage service for data you rarely access. Like putting old documents in a warehouse - cheaper to store but takes time to retrieve.
A company stores old employee records in Glacier for compliance, accessing them only when legally required.
All are low-cost, long-term object storage options for rarely accessed data. They trade lower storage price for higher retrieval latency and additional retrieval/early-deletion fees. AWS implements Glacier as S3 storage classes (managed through S3 APIs), while Azure uses an access tier on Blob Storage, and GCP/OCI use archive storage classes/tiers.