A Floppy Disk is a removable piece of media that allows you to write data to it for storage.
The two most common types of Floppy Disk were the 5 1/4", which is now predominantly defunct, and the 3 1/2" disk which is still in wide use.
The 5 1/4" disk was offered in two formats that held either 360KB or 720KB. The 3 1/2" floppy holds 1.44 MB of data.