What is the importance of secondary storage?

Secondary storage can be used to restore a backup of your files if you have to format. You can use it if you run out of room on your main hard drive. If it is external secondary storage you can also bring it with you if you need to access files at work or somewhere else.

Commonly used types of secondary storage are the USB drive and Floppy Disk, as referred to in the joke 'Can you turn my floppy disk into a hard drive?' which is impossible!