Very oversimplified, the Noise Texture is a sine-based Noise and if you increase the detail from 1 to 2, you combine the Noise with a smaller version of itself (recursion), the Scale of that smaller Noise is 2 times the Scale of the original. With Detail set to 3, it’s combined with yet another Noise, this time with a Scale 4 times the original, etc.
That factor 2, is the Lacunarity. So, setting the Lacunarity to 1, means you are combining the Noise with itself and changing the Detail will have no effect.
