“File Associations” is a simple, but important concept that everyone who uses operating systems should know. Let’s start by defining operating systems, files, and programs.
An operating system is the “main program” that runs when you start up your smartphone, tablet, laptop, or desktop. The popular ones are Windows, OS X, Android, iOS, and Linux.
Files and folders are the building blocks of the information that is stored on your device. The files can be categorized as operating system files, program files, or data files.
Programs (or “Apps”) are specific files that are “executable” … that is: they run within the operating system, manipulating the screen, speakers, files, and folders.
Data files are files “indirectly” created by you: like pictures, documents, email, and contacts. I say indirectly, because you are actually manipulating the programs to create, view, or edit those data files.
With those definitions in mind, I can clearly describe a file association: When you click to open a data file, the operating system needs to know what program is associated with that type of data file. For example, when you click to open a PDF file, the operating system needs to know if it is supposed to open it with Adobe Reader, Edge browser, or any number of other PDF viewers that may be on your device. This concept applies to DOC files, HTML files, JPG files, and all the rest.
This brings up another topic: “How do you change a file association”?
File associations can get changed when you load a new program, load a new operating system, or (unintentionally) load malware … so you may want to change them back to your preferred programs. For example, this happens a lot with Windows 10: it “takes over” by associating your browser/email/picture/other files with their preferences, not yours. Now that you have the concept and the nomenclature, you can figure out how to change them back: simply Google “change file associations Windows 10” and learn how to change them back. For other operating systems, simply change “Windows 10” to the name of your device’s specific operating system.