Abstract: Mathematicians don't just do mathematics.
We communicate our subject too, by speaking, writing, teaching, illustrating, editing, explaining, and professing it, for expert and non-expert audiences alike. Words, pictures, equations, and other media may be well or poorly suited to the special purposes of mathematical exposition, and mathematical exposition may be good, bad, or indifferent, depending largely on its audience. But, as I will argue with examples, many from history, mathematical exposition is at its best real and valuable mathematics --- and no less challenging or deserving of professional reward than other forms of mathematical activity.
Mathematics is a big tent, and its vitality and growth depends on contributions from many directions.