What is backing storage made up of?

Backing storage, also known as secondary storage, is made up of various non-volatile storage devices that retain data when not in use. Common examples include hard disk drives (HDDs), solid-state drives (SSDs), optical discs (like CDs and DVDs), and flash drives. Unlike primary storage (RAM), backing storage provides larger capacity and persistence for data storage, making it essential for long-term data retention and retrieval.