External memory

Non-volatile, secondary storage: This technology provides massive, disconnectable data capacity outside a computer's main memory for backup, archiving, and transport.

External memory, correctly termed auxiliary or secondary storage, handles all persistent data not housed in the system's primary RAM. It's mission-critical for data integrity and scalability (up to 10+ terabytes). Key implementations include portable Solid-State Drives (SSDs) and Hard Disk Drives (HDDs), which connect via high-speed protocols like USB 3.2 or Thunderbolt 4. Enterprise-level solutions leverage Network-Attached Storage (NAS) and Storage Area Networks (SANs) for centralized, redundant access. This system ensures data remains available and secure, even when the primary host is powered down.

https://en.wikipedia.org/wiki/External_storage