An application that is designed to serve the needs of all its users often gets accessed from different sources. For instance, an android application can be accessed from a blackberry device which creates a situation in which the compatibility of the platforms becomes a rather tricky issue. In order to install android apps on a blackberry device, you will need to allow installation of apps from unknown sources and the APK file that has the application. This is one of the typical examples of apps that can work across platforms and serve all your needs without you having to worry about the platform you are on.
In other scenarios, the platform compatibility of any application that you are using will be on the user agent it deposits on your browser if it is a web application. A web application can be used from any platform that has an internet connection and some of the applications even allow for working offline and this means that once you have gained initial access of the application, you can even turn off your internet connection and continue with your other activities which will be backed up to the web servers once you have re-established an internet connection.
The creation of applications that are compatible across platforms enables the users to be able to use the application from wherever device or operating system they are working from. The users will be able to enjoy all the features that are on the application with no fear of where they are accessing this application or what device they are running it on. There are a ton of libraries that are designed with the intention of creating a universal application running platform in which applications can be run across platforms without developing issues. This is the same case with operating systems which can be run on both hardware and software.
For the operating systems, running them across platforms requires the creation of a virtual machine which gets to be run in a sandbox or controlled environment and in there, you get to enjoy all the features of the operating system and even install applications specifically designed for it. It is very easy to run virtual operating systems in foreign environments and this ensures that you still have the familiar operating mechanisms and principles on which to work with and process information the way you are used to.
For any program, being compatible across platforms means being accessible to everyone that has an interest in the application as well as serving the needs of more users. Software developers that need to reach more people usually create universal versions of their apps and use this approach to ensure that every one of their customers gets to enjoy the app experience they have prepared for them. It is for this reason that a lot of developers will try to create the simplest version of their application and port it across all the platforms they would like to see their users making use of their apps.