According to True-VDB documentation and Blender Market tutorials:
: Includes approximately 10 assorted VDBs (requires ~9GB of storage).
: After enabling, the add-on may prompt you to install a 7zip engine within the interface to handle large file decompression. Restart Blender after this step.
: Includes all Season 1 assets, totaling up to 55 VDB sequences (requires ~110GB of storage).
The file (or related .zip versions) typically contains the True-VDB v1.1 add-on and asset library for Blender, developed by True-VFX . This version was a major update that introduced cross-platform support for both Intel and M1 Macs and a redesigned "from the ground up" pack installation system. Overview of True-VDB v1.1
: VDB (Volume Database) is an industry-standard format for storing sparse volumetric data efficiently, reducing memory usage during complex simulations.