What is a Multiband Compressor? // How do you use a Multiband Compressor in Premiere Pro CC

What is a multiband compressor?  How do you use one?  Why, in fact, would you use one?  Multiband compressors are a beautiful 2 for 1 in the audio processing tool world.  They combine the dynamic range decreasing power of a compressor, and combine that with the sound shaping world of the Equalizer.  The way they accomplish this is by using 3 or 4 individual compressors on different frequency bands across the whole EQ spectrum.  This is powerful because you can compress different frequencies at different amounts, shaping the tone while compressing the amplitude.