Avatar -2009- Extended -2160p- Uhd -bd- Dv Hdr ... -

This refers to the Special Edition or Extended Cut of the movie.

This identifies the film. The year (2009) is included to distinguish it from the sequels (like Avatar: The Way of Water). Avatar -2009- EXTENDED -2160p- UHD -BD- DV HDR ...

Stands for High Dynamic Range.