Secondary storage is also known as external memory, secondary memory or auxiliary memory. It is non-volatile storage, which means it does not lose data then the device is powered off. It is also not directly accessible by the CPU and it is not accessed using input / output channels.
Secondary memory is cheaper and larger than the Primary storage. Secondary storage devices have more access time because they are external devices. The read and write speed of the Secondary storage is also less in comparison to that of the Primary memory (RAM, Cache, Registers). Flash Drives, USB Thumb or pen drives, memory cards, Hard Disk Drive (HDD) and Solid Sate Drive (SSD) are examples of Secondary storage. It also sometimes called as permanent storage.