building blocks of android application

To understand the basics of an android application and how it works, first we need to understand these terms.

Activities: This is the atomic functionality. An activity is usually a single screen in the application. When associated a UI it will be similar to a page/form of other platforms. There exists a stack of activities that is maintained by the activity manager. Every activity in android is associated with a class. It runs/exectues in the process that creates it.

Intents : Android uses a class called 'Intent' to move from screen to another. It has the information describing the action, data etc.

Intent Filters: specifies what the activity is capable of handling.

Service: Service is the one that performs a particular task for another applciation. Application which makes use of this service runs on different processes. Since they run on different context/process it makes use of Binder IPC for the communciation.

Content Provider: This is normally used for accessing lower level functionality like file access, network access etc. The content provider provides the platform related functionality to the running application.

Task: This contains a collection of related Activites. These set of activities perform a particular task. This is comparable to an application on other platforms.

Process: This is a simple linux process.