https://support.google.com/accessibility/android/answer/6007100?sjid=11601831860395712703-EU

TalkBack is an accessibility feature that helps people who are blind or have low vision to interact with their Android devices using touch and spoken feedback.

When TalkBack is on, items on the screen are outlined with a focus box, and the device gives audio cues about what is on the screen. Instead of typical touch interactions, you can navigate the device through TalkBack gestures. To learn TalkBack basics, watch a video.

Tip: To turn on TalkBack, options vary based on the device manufacturer, Android version, and TalkBack version. The information below applies to most devices, but you might experience some differences.

When you set up your phone

During phone setup, hold down both volume buttons for a few seconds to turn on TalkBack. You can continue using the volume keys as a shortcut to turn TalkBack on or off once you’re done setting up.

Tip: To permanently turn off the volume key shortcut after setup, go to Settings Accessibility TalkBack. Select TalkBack shortcut and turn it off to disable it. Learn how to change your TalkBack shortcut.

After you set up your phone

Option 1: Use device settings

1. On your device, open Settings .
2. Tap Accessibility TalkBack.
3. Select Use TalkBack.

After you turn on TalkBack, control your device with TalkBack gestures.

Option 2: Use accessibility shortcuts

With the accessibility shortcut turned on, you can use it to turn TalkBack on or off with an on-screen button or physical keys.

1. On your device, open Settings .
2. Tap Accessibility TalkBack TalkBack shortcut.
3. Turn on TalkBack shortcut.
4. To set up shortcut preference for your device model, follow the on-screen instructions. You can also learn more ways to configure the accessibility shortcut.