Texture packs usually come in .zip format. Make sure not to unzip the file, as Minecraft requires it to be zipped.
: A critical text file that tells Minecraft the pack is a valid resource. It includes a "pack format" number (which corresponds to your Minecraft version) and a description that appears in the game menu.
Texture packs, also known as resource packs, change the appearance of the game. They modify the textures of blocks, items, mobs, and the user interface. How to Install Texture Packs Safely