Amplitude describes something there is a lot of, or abundance. If people compliment the amplitude of emotion in your poetry, it means you put much emotion into what you write.
The noun amplitude describes the depth, breadth, or magnitude of something — in other words, how big or full it is. It comes from the Latin amplus, "large, spacious." You can admire the amplitude of your favorite teacher's intelligence or try to guess the amplitude of a snow storm. In physics, amplitude is a change in oscillation or vibration, and in math it's the angle made with the positive horizontal axis by the vector representation of a complex number.