Uses of Wien's law of displacement

So, let's start with the formal definition of peak wavelength. Peak wavelength $(lambda_{max})$ is the wavelength where an object absorbs the most photons (or, to our eyes, becomes more dark, or, at a darker point, completely isn't in the visible spectrum. (for a refresher, take a look at the electromagnetic spectrum, and here's something to look at as you go: electromagnetic spectrum)

Well, back to your question, why do we even have $lambda_{max}$, and what is it used for? So, I did a bit of research in an astrochemistry textbook that I have, and found a reason why peak wavelength is useful. It is useful as a parameter to compare the quality of several types of molecules.

Hopefully this was helpful in answering your question!