If an app wants to access data and functions outside of its own area, it needs the permission of the system. Android differentiates between "normal" permissions that do not require authorization and "dangerous" permissions that do require authorization.  

If you install an app, the app is automatically given a number of "normal" permissions that do not require authorization. For example, the permission to create an icon or to use the Internet. If the app requires additional permissions, it will ask for your agreement before downloading or during use.

For example, if you want to send a voice message via WhatsApp for the first time, you must give the app permission for the microphone. You can enable / disable these "dangerous" permissions at any time in the settings.

Note: To see which permissions the app needs before installation, you have to scroll down in the Play Store on the download page under "About this app ->" and "see more" of the "App permissions".

1. Open the Settings

2. Apps & notifications

3. See all Apps

4. Choose a App

5. Permissions

6. You can enable/disable the permissions with the switches