When you use most programs, you need to save data. That way, the next time you need the data, you can use or modify it without having to retype everything all over again.
For example, if you’re writing a letter or a report on a word processor, you want to save that letter or report so that you don’t have to retype the entire letter or report. Whenever you save data in a program, the program saves it in a file.
A file acts like a box that holds your stuff. If you write a letter in a word processor, that file contains your letter. If you type a list of names and addresses in a database, ...