Signed Distance Function - 3D Plane

Question

I truly love IQ's page and the information within regarding SDF's:
(https://www.iquilezles.org/www/articles/distfunctions/distfunctions.htm)

I have a few figured out but but his sdPlane is getting me..

float sdPlane( vec3 p, vec4 n )
{
  // n must be normalized
  return dot(p,n.xyz) + n.w;
}  

He doesn't identify what the input 'n' is being used for and I am not the greatest in math.
Something like the Width, Height, Depth from point p, but then n.w doesn't make sense..

Any help will be awesome, Thanks!

Answer 1

n is a Plane Equation. .xyz is the normal vector of the plane and .w is the distance from origin.