That varies with OS, but FAT is currently the most common for floppies.
Floppy disks use a FAT file system.
FAT12
Any file system can be used by a floppy disk, as long as the minimum partition size of the file system does not exceed the capacity of the floppy. FAT12 is the most common on Windows / MS-DOS computers. AFS was common on earlier Macs. ext was used among many Linux users. Floppy disks can use a variety of file systems. On MS-DOS and Windows computers, the primary file system for floppies is FAT12. On older Macs, the file system was HFS or MFS. Linux computers sometimes use ext.
You use My Computer & Windows Explorer to browse the file system on a drive in Windows XP.
Windows 2000 will automatically use the FAT32 file system
"File Explorer".
Use a floppy drive, drag and drop the files you want. The space you have though will be extremely limited, as your using a floppy drive
After you make the floppy disc a boot drive (beforehand), you can use it to boot your system when you are unable to boot using your harddrive.
If your system has a floppy drive you can use another computer to place the needed driver on a floppy disk an then reinstall them.You could use a USB drive to transfer the drivers to the computer if no floppy drive is present.There are also several ways to connect a second computer to the faulty system so the needed drivers can be transferred and installed.
No Macintosh has included a floppy drive since the release of the iMac G3 in 1998. If you need to use a floppy disk, you will have to purchase an external USB drive.
format
On a modern Microsoft Windows computer, the most frequently used file system is NTFS.