In the modern and dynamic mobile world there are a lot of applications. If every application works by its own rules – main buttons located in different places and the reaction of the application is unexpected and unusual, the user will spend some time learning how the app works and get used to it. Also, a new functional of an application will probably contain a lot of bugs that will block the work of the main functional or can even be dangerous for the mobile device. Due to this reason, the stores of different platforms, such as AppStore and PlayMarket have some list of requirements for the applications before posting them online. These requirements are mostly based on the guidelines - a collection of the rules that are required to be applied while creating the application. They are the layout design requirements, user feedback principles, that the developer must follow while designing the app.
Guideline is a list of recommendations, rules, principles from the developers of the mobile platform, operating system with the help of which the applications look and work properly on each of these operating systems and platforms. Human Interface Guidelines is used for apps on the iOS platform and respectively Material Design is used for Android.