Robert Conner asked me to define the various words for different types of programs.
Tech proliferates words like flies proliferate eggs. And they can be just as hard to track.
Here's a quick refresher on common terms for the larger program categories:
Application: A program that turns your computer into a specific tool, such as a word processor, photo editor, or browser. Generally, people buy computers so they can run applications. (They also buy computers for play, but I figure you don't need a definition of the word game.)
Utility: A program that either protects the computer or makes it faster, more reliable, or easier to use. No one buys computers to run utilities; there's no point to them unless you already own a computer.
Suite: A collection of applications or utilities sold for a single price, and hopefully with a single user interface. These include both application suites (Microsoft Office), and utility suites (Norton Internet Security).
Add-in, Add-on, Plug-in, Extension: Four terms for what are effectively the same thing--a program that runs inside of, and augments, another program (usually an application). You probably have a few add-ins running in your browser (Flash, for instance, or one or more toolbars), and perhaps some in Office or a photo editor.
App: A program written for a mobile operating system like iOS or Android. Despite the name, apps aren't necessarily applications. Some are games, utilities, or suites.
Contributing Editor Lincoln Spector writes about technology and cinema. Email your tech questions to him at firstname.lastname@example.org, or post them to a community of helpful folks on the PCW Answer Line forum. Follow Lincoln on Twitter, or subscribe to the Answer Line newsletter, e-mailed weekly.