What is the difference between Android 5 and Android 6?

1. Runtime Permissions: In Android 6, the ability to request permissions from the user not at the time of app installation, but immediately before the functionality requiring permission is used, was introduced. This gives users more control over their data and resources.

2. Doze Mode: A new power management mode that defers background activity (network requests, synchronization) when the device is inactive for a long time and the screen is off, significantly saving battery life.

3. App Standby: Optimization for inactive apps. Apps that are not used for a long time are partially restricted in background activity, which also helps conserve battery.

4. Fingerprint API: Official support for fingerprint authentication for use in applications.

5. Direct Share: Allows apps to provide shortcuts for quick sharing of content with specific contacts or conversations in other apps.

6. App Links API: Improved handling of web links, allowing them to be opened directly in the corresponding app if it is installed and configured.

7. Granular Notification Controls: Users gained the ability to more precisely configure which notifications they want to receive sound alerts and vibrations from, and which they do not.

8. Enhanced Context Menu "Select All": When selecting text with a long press, a context menu appears with options "Cut," "Copy," and "Paste." In Android 6, an "Assist" (formerly "Now on Tap") option was added, allowing users to get contextual information about the selected text.

9. Auto Backup for Apps: The system automatically creates backup copies of app data (such as settings and small files) on Google Drive.

10. Changes in Camera API2: Continued development of Camera API2, providing more detailed control over camera hardware capabilities.

The key differences focus on improved power management, a more flexible permission system, and enhancements in user interface and system APIs.