Interapplication communication
Apps in Android cannot access each other's data directly because of application sandboxing, but Android's system provides some other mechanisms for the applications to communicate with each other. Intents and content providers are mechanisms that we can use on the Java API layer. Intents and content providers should be used carefully to prevent attacks from malware applications. This is the reason why it is important to understand their characteristics.
Intents
Intents are an asynchronous interprocess communication mechanism. Intent is a message that includes the receiver and optional arguments to pass the data. The receiver of Intent can be declared explicitly so that the Intent is sent to a particular component, or it can be declared implicitly so that the Intent is sent to any component that can handle it. Intents are used for intra-application communication (in the same application), or for interapplication communication (in different applications...