Applin is a framework for making mobile apps. It uses server-driven UI. If you know computer programming, you can use an Applin server library to make an app server, with pages and functions defined in the servers code. Then use the Applin client library for iOS to quickly make an iOS app that connects to your server and displays the pages.
Applin Tester embeds the Applin client library for iOS and connects to any Applin server. As you develop your app server, you can use Applin Tester to connect to your server and display your apps pages. Applin Tester also displays Applin demo apps, with links to their source code.