Alberto Brandolini explains Event Storming and its advantages in a blog post, and he does it far more succinctly than we could.Event Storming is a workshop format for quickly exploring complex business domains:

• It is powerful: It has allowed me and many practitioners to come up with a comprehensive model of a complete business flow in hours instead of weeks.
• It is engaging: The whole idea is to bring people with the questions and people who know the answer in the same room and to build a model together.
• It is efficient: The resulting model is perfectly aligned with a Domain-Driven Design implementation style (particularly fitting an Event Sourcing approach), and allows for a quick determination of Context and Aggregate boundaries.
• It is easy: The notation is ultra-simple. No complex UML that might cut off participants from the heart of the discussion.
• It is fun: I always had a great time leading the workshops, people are energized and deliver more than they expected. The right questions arise, and the atmosphere is the right one.

If you want to know more about Event Storming, check out Brandolini's book, Introducing EventStorming.