This document discusses API communities and what they mean. It defines a community as a group of interdependent organisms or people sharing common goals. API communities bring together API providers and developers around common tools and goals. When the goals of the community members are aligned through cooperation and opportunities, everyone benefits - the company through revenue and customer retention, and developers through easier work and increased productivity. For the community to succeed, the community builder must devote significant resources to tracking metrics like exposure, usage, sales, and sentiment in order to analyze and adjust the community over time.