Android Tutorial - Android Development Guru

An Activity is an application component that provides a screen with which users can interact in order to do something, such as dial the phone, take a photo, send an email, or view a map. Each activity is given a window in which to draw its user interface. The window typically fills the screen, but may be smaller than the screen and float on top of other windows.[1] http://developer.android.com/guide/components/activities.html [1 ] An Activity is a screen in which user perform some task. It might be capturing image, dialing phone number, typing text message etc. These all are the activities. Almost every screen with which users interact is an activity.