From EventStorming website:

EventStorming is a flexible workshop format for collaborative exploration of complex business domains. It comes in different flavours, that can be used in different scenarios. The adaptive nature of EventStorming allows sophisticated cross-discipline conversation between stakeholders with different backgrounds, delivering a new type of collaboration beyond silo and specialisation boundaries.

1. Sticky notes (a lot of them, with different colours)
2. Pens
3. A lot of horizontal space (or a paper roll)
4. Facilitator
5. Domain Experts
6. Stackeholders
7. Intorduction about the problem the scoping session needs to solve

Official website
Blog post from Alberto Brandolini (The inventor of Event Storming)
YouTube talk about EventStorming