The development of mobile applications for smartphones and tablets is known as app design and development. It involves developing the code, designing the user interface, testing the application, and publishing it to the app store. While app development entails writing the code that makes the app work, app design entails creating a layout that is both visually appealing and user-friendly. Testing an app involves ensuring that it works properly on various devices and operating systems. The app can be released to the app store for users to download and use once it is finished, but it needs to be updated and maintained on a regular basis to stay current.