Needless to say, if the Operating System (the OS ) just wrote a bunch of bytes on to the hard disk without any kind of organization, there would be problems as soon as you wanted to write some more bytes for some other document.

So, the OS gives each collection of bytes a name, and keeps a record of the name and which bytes belong to the name. This named collection of bytes is called "a file" by analogy to a file stored in a filing cabinet.