For instance, if you need to analyze color you need a spectrometer that covers the visible spectrum from approx. 400 – 700 nm.
The resolution is the spectrometer’s ability to distinguish between two closely spaced wavelengths. So, if your spectrum has some sharp peaks that are separated by say 0.5 nm or more, you need a spectrometer with at least 0.5 nm resolution.
Some applications (like Raman and IR spectroscopy) will not list the wavelength range and resolution …