Popular assets like the Advanced Vertical Fog Shader in the Unity Asset Store or Unreal's Exponential Height Fog provide several "Advanced" features:
Calculates fog density by sampling the Depth Texture to reconstruct world-space positions and applying a vertical gradient. Download File Advanced Vertical Fog Height Fog ...
Simulates "God Rays" by allowing light to scatter through the fog particles. Popular assets like the Advanced Vertical Fog Shader
Uses textures or procedural noise to create a "wavy" or "fluffy" cloud effect rather than a flat gradient. Download File Advanced Vertical Fog Height Fog ...