Explain why you would format a floppy disk?

Theoretically - it erases all the data on the disc - However...

On a floppy disk, there is a 'reference track' which holds details of each file on the disc (name, start point, size and end point) When you format a disc - the computer ONLY erases the details on this track. Without the reference track information, there is no way for the computer to locate a file.