App (Application).

The word app became part of everyday language with the iPhone and the App Store from 2008 onwards, but it is older: it is simply short for application. An app differs from a website in that people use it to do something, not just to read something. They log in, enter data, trigger processes and see results that depend on their own input. Whether this program is installed from a store or runs in the browser is a technical question, not a fundamental one.

Today, four types are mainly distinguished. A native app is written for one platform, such as iOS or Android, and installed from the store. A cross-platform app is built from a shared codebase for several platforms. A web app runs in the browser without installation. And a progressive web app (PWA) is a web app that can be added to the home screen like an app and can receive push notifications. To users these types feel similar; for the business they differ greatly in cost, maintenance and distribution.

For companies, the most important question is therefore not 'Do we need an app?' but 'Who should get what done with it, and where?'. A restaurant that wants reservations to arrive on the phone instantly does not need a store app; a PWA with push is enough. A business whose technicians record job reports in basements without reception, on the other hand, needs an app that works reliably offline — and a native app does that better. And a business that above all wants to be found often needs no app at all, but a good mobile website.

Almost every business app also consists of two parts: the interface on the device and a backend on the server that stores data and exchanges it with other systems. Anyone planning an app is therefore always planning this backend too, even though it never appears on a screen.