The spectral range defines the visibility of light.
When we talk about the spectral range, we usually mean the light spectrum. This is differentiated into different wavelengths.
Depending on the wavelength, we refer to the visible spectral range of light and the spectral range of UV light, the portion of the electromagnetic spectrum which is not visible to the human eye.
We also refer to spectral ranges in laser technology, as lasers produce light beams. These light beams are not within the visible spectral range for all types. The evaluation of the performance of a laser also depends on the spectral range.
The light spectrum visible to the human eye includes all perceptible colours that we can differentiate. What is important here is that we do not need any aids or tools to cover this spectral range.
By the way: Naturally the human perception of the light spectrum has been scientifically standardised. Just making sure that everything is well regulated.