What types of permissions exist in Android and how do they differ?

In Android, there are three main types of permissions:

1. Normal permissions:

   • Do not pose a threat to user privacy or device operation.
   • Automatically granted by the system upon app installation.
   • Examples: internet access, changing sound settings.

2. Dangerous permissions:

   • Can affect user privacy or device functionality.
   • Require explicit user approval at runtime.
   • Examples: camera access, contacts, location.

3. Signature permissions:

   • Granted only to apps signed with the same certificate as the app declaring the permission.
   • Used for communication between apps from the same developer.

Difference in risk level and granting method: normal permissions are granted automatically, dangerous permissions require user consent, and signature permissions are only for trusted apps.