HDR stands for High Dynamic Range and is a function to better display images with high contrast. on LG smartphones, HDR is set to Automatic by default. this means that the camera itself decides when HDR should be used. HDR can also be permanently enabled or disabled.

Android 9 | LG UX 9.0
HDR -  Open the  Camera -App
HDR -  Open the  Settings
HDR -  Tap on  HDR
HDR -  Choose between  Auto ,  On  and  Off
  1. Open the Camera-App
  2. Open the Settings
  3. Tap on HDR
  4. Choose between AutoOn and Off

LG Instructions