In a part-18 file for an HD texture pack, you would likely find:

You cannot open or view this content effectively without having all other parts (part01 through the final part) in the same folder, as WinRAR or 7-Zip needs the complete sequence to extract the data.

: Large .dds or .png files containing the "color" layer for 4K textures (e.g., weathered stone, detailed wood grain, or ornate metal).

: Texture layers that define how light interacts with surfaces to create the illusion of 3D depth and bumps without adding polygons.

Since "HD-Texture-Pack.part18.rar" is typically one piece of a large, split archive, the content inside is usually a continuation of high-resolution image files and configuration data.

: Small scripts or .json files that tell the game engine how shiny, rough, or metallic a specific texture should appear.