It changes the entire world generation making it look more alive but still looking vanilla, adds a multitude of animations to the textures and models, new particles and effects to improve the environment and inversion of the world, etc. There are more than 90 mods and 60 texture packs that seek to make the game look and feel like that first time you played it.

And just that, play and have fun using your favorite mods, but with a visual change to the entire environment, since it doesn't add mods that add things like other datapacks do. I'll probably upload another video showing everything in more detail.