What is an Intent, and what is the difference between explicit and implicit intents?

An Intent is a messaging object describing an operation to be performed. It is how Android components communicate, including across app boundaries.

• An explicit Intent names the exact component to start, by class. Used for navigation within your own app — starting your own Activity or Service. It is unambiguous and secure, because you know exactly what will handle it.
• An implicit Intent declares an action and lets the system find a component that can handle it. Sharing text, opening a URL, dialling a number, or picking an image. The system matches the action, data, and category against the intent filters declared by installed apps, and shows a chooser if several qualify.

// Explicit
startActivity(Intent(this, DetailActivity::class.java))

// Implicit
val intent = Intent(Intent.ACTION_VIEW, Uri.parse(url))

Practical points that matter:

• Always handle the case where nothing can handle an implicit Intent, or the app crashes with ActivityNotFoundException.
• Package visibility since Android 11 means you must declare <queries> in the manifest to see which apps can handle certain intents.
• Never send sensitive data in an implicit Intent — any app with a matching filter can receive it.
• PendingIntents must specify mutability (FLAG_IMMUTABLE or FLAG_MUTABLE) from Android 12, and immutable should be the default.