What is An Activity in Android?
Android activity is the subclass of ContextThemeWrapper class. It is a single screen with a user interface, similar to a window or frame of Java.
It is the screen that the user sees, where the information is presented. It is also the starting place where any activity can be launched. It also allows the developer to place all of the UI components or widgets in a single screen.
An activity class loads all the UI components using the XML file available in res/layout folder of the project. An application can have one or more activities without any restrictions. One can easily switch between the activities during runtime of the application. However, every activity for that application should be declared in the AndroidManifest.xml file and the main activity for the application must be declared in the manifest with an <intent-filter> that includes the MAIN action and LAUNCHER category.