What is the different between Explicit and implicit activity call in android?

For example:

implicit activity call

In intent filter you create action for you activity, so other app can call your activity via this action as following:

<activity android:name=".BrowserActivitiy" android:label="@string/app_name">
   <intent-filter>
      <action android:name="android.intent.action.VIEW" />
      <category android:name="android.intent.category.DEFAULT" />
      <data android:scheme="http"/> 
   </intent-filter>
</activity>

And the other way to call implicit Intent is below:

Intent intent = new Intent(Intent.ACTION_VIEW, Uri.parse("http://www.example.com"));
startActivity(intent);

Explicit activity call

You make a call that indicate exactly which activity class:

Intent intent = new Intent(this, ActivityABC.class);
intent.putExtra("Value", "This value for ActivityABC");
startActivity(intent);

Hope this help you understand more about Explicit and implicit activity call in android.

You can get more detail about Android Intent here

Every time I get confused among these in either interview. So, I have summarised it like this, may it help someone to keep this difference in mind.

Summary:

In Implicit Intents, the user implicitly tells the system WHAT should be done, without specifying who should do.

In Explicit Intents, the user explicitly tells the system WHOM to be triggered for whatever the work is.

1. Explicit Intents are used to call a specific component. When you know which component you want to launch and you do not want to give the user free control over which component to use.For example, you have an application that has 2 activities. Activity A and activity B. You want to launch activity B from activity A. In this case you define an explicit intent targeting activityB and then use it to directly call it.
2. Implicit Intents are used when you have an idea of what you want to do, but you do not know which component should be launched. Or if you want to give the user an option to choose between a list of components to use. If these Intents are send to the Android system it searches for all components which are registered for the specific action and the data type. If only one component is found, Android starts the component directly. For example, you have an application that uses the camera to take photos. One of the features of your application is that you give the user the possibility to send the photos he has taken. You do not know what kind of application the user has that can send photos, and you also want to give the user an option to choose which external application to use if he has more than one. In this case you would not use an explicit intent. Instead you should use an implicit intent that has its action set to ACTION_SEND and its data extra set to the URI of the photo.

An explicit intent is always delivered to its target, no matter what it contains; the filter is not consulted. But an implicit intent is delivered to a component only if it can pass through one of the component's filters