The word has become ubiquitous. The iPhone has apps, Android devices have apps, the Chrome browser has apps and now Mac OS has apps too. So what are they? How can they be the same things in all these places? What if you want one of your own?
I’ll start by lifting a convenient definition from Wikipedia like all good web authors these days
“…a lightweight application, tailored to a device’s form factor and input-output interfaces (key pad, touch pad, remote control, display, etc)”
Not bad but we need more specifics. App is short for application which is a term that’s been used in computing since the invention of programmable computers. Sometimes called application software it pretty much means a computer program used by a person to do a thing (as opposed to programs that talk to each other, park a car, or ID faces without a person running it).