What is difference between ‘violet’ and ‘purple ?

Purple is more reddish and saturated, while violet is more bluish and less saturated.

We see neither the ultraviolet wavelengths and shorter, nor the infrared wavelengths and longer. How do we see the rest? We have three types of colour-sensitive cells in our eyes, so-called cones.The cones don’t perceive just a single wavelength; they are activated by a whole range of wavelengths, and the signals received from the cones are then processed by the brain in such a way that every colour can be thought of as composed of three different elementary signals.

When a mixture of photons that have different wavelengths hits the retina (creating a ratio of red, green, and blue activation different from any spectral colour), the brain will perceive it as an entirely different colour. For example, there is no white wavelength. What we perceive as “white” is in fact just a mixture of many different spectral colours.When violet light hits the retina, both the “blue” path and (much less) the “red” path are activated. The brain interprets this kind of input in a specific way, which we call “violet”.

Purple is formed by mixing red and blue in a ratio close to 1:1, whereas violet is perceived by your eyes as containing more blue than red.

To us, humans, purple looks like a more saturated shade of violet, but violet objects in nature are fundamentally different from purple ones. Purple objects are “red and blue at the same time”, whereas violet objects are… just violet.