What is a texture pack?

Texture packs are modifications to the look of Minecraft, altering the textures of blocks and mobs in the world and occasionally the UI as well. Sometimes texture packs will look utterly different to Minecraft's original textures, giving worlds a different feel or theme, be it sci-fi, fantasy or something else.

Texture packs also change the designs of items and armours to match the overall look of the world.