Filters separate different parts of the electromagnetic spectrum by absorbing or reflecting certain wavelengths and transmitting other wavelengths.
Color filters are glass substrates containing absorbing species that absorb certain wavelengths. A typical example is a cut-on color filter, which blocks short wavelength light such as an excitation source, and transmits longer wavelength light such as fluorescence that reaches a detector.
Interference filters are made of multiple dielectric thin films on a substrate. They use interference to selectively transmit or reflect a certain range of wavelengths. A typical example is a bandpass interference filter that transmits a narrow range of wavelengths, and can isolate a single emission line from a discharge lamp.