Your computer must have at least one storage drive to function. Usually, the storage drive is an internal drive; located inside the computer case. Internal drives come in a variety of storage sizes and can be replaced if you don't have enough storage space. You can set up a computer with an external drive in addition to the internal drive. An external drive attaches to the computer, generally through a USB port. An external drive gives you more storage space for backup files, pictures, music, or particularly large files. External drives are also portable; you can move them between computers. This will allow you to share things like pictures more easily.