Physical Drives

• A physical drive is a piece of hardware that reads data from, and often has the ability to write data to, a particular medium. These can be a magnetic or solid state hard drives, DVD or CD ROM drives, USB flash drives or even older floppy drives. These physical drives are either self contained units, such as flash drives or hard drives, or read from a removable disks which you insert into the drive itself.
  
  

ISO

• An ISO is a type of file format that is also known as a "disk image." This is because the file format is used to create the physical disks to put into disk drives. You put the files you want to appear on the final physical disks together and encode the group as an ISO file. You can then burn these files to a disk. When the disk is inserted into a disk drive the files in the ISO file will be the disk's contents.
  
  

Creation

• Users need special software in order to create ISO files, and to use a specific burning function to make disks from the ISO files. To make a disk from the ISO, you need to specifically burn the disk image, not just the file itself. If you just burn the ISO file, the result will be a disk with only the ISO file. On Windows 7, you would burn the disk image by right-clicking the ISO file and selecting "burn disk image."
  
  

Uses

• Whereas information can shoot through cyberspace instantly, items in the material world, such as program or operating system disks, take time to travel from place to place. However, ISO files allow you to get your hands on disks much faster than waiting for them to come through the mail. You can simply download the ISO then burn the image to a CD or DVD with the physical optical drive.