The .rar extension indicates that the files have been compressed using WinRAR. This format is preferred for "custom packs" because:
To access the contents of a .rar file, you cannot use the default tools built into Windows or macOS. You will need a third-party extractor: custom pack.rar
: A collection of Photoshop brushes, Lightroom presets, or vector graphics for digital artists. custom pack.rar
: Follow the specific instructions for the software you are using. For instance, Minecraft resource packs usually need to be moved to the %appdata%\.minecraft\resourcepacks folder. A Note on Safety custom pack.rar