Putting it simply:

As the name suggests, it's the context of current state of the application/object. It lets newly-created objects understand what has been going on. Typically you call it to get information regarding another part of your program (activity and package/application).

You can get the context by invoking getApplicationContext(), getContext(), getBaseContext() or this (when in a class that extends from Context, such as the Application, Activity, Service and IntentService classes).

Typical uses of context:

  • Creating new objects : Creating new views, adapters, listeners:

    TextView tv = new TextView(getContext());

    ListAdapter adapter = new SimpleCursorAdapter(getApplicationContext(), ...);

  • Accessing standard common resources : Services like LAYOUTINFLATERSERVICE, SharedPreferences:

    context.getSystemService(LAYOUT_INFLATER_SERVICE)

    getApplicationContext().getSharedPreferences(name, mode);

  • Accessing components implicitly : Regarding content providers, broadcasts, intent

    getApplicationContext().getContentResolver().query(uri, ...);