Effective altruism is a philosophy and a growing global community which applies evidence and reason to determining the most effective ways to improve the world.

It’s about combining both the heart and the head: compassion guided by data and reason. EA is about dedicating a significant part of one's life to improving the world and rigorously asking the question, “Of all the possible ways to make a difference, how can I make the greatest difference?”

A more detailed explanation of Effective Altruism can be found here.