When more than one team is involved in a project it becomes necessary to ensure synchronisation between the multiple teams. The Scrum of Scrums meeting is the process for ensuring this synchronisation. As with the Scrum meetings it is an opportunity to provide updates, discuss challenges faced and coordinate activities.
Each Scrum team must be represented. The person attending should ideally be a technical person rather than the Product Owner or Scrum Master. Though if the number of teams involved in the project is small then there can be advantages in sending two people along, one of whom could be the Product Owner or Scrum Master. The person attending should be chosen by the team based on who has the best understanding of the topics being discussed at that point in the project. Therefore the person representing a Scrum team at the Scrum of Scrums may change as the project progresses.
Like the daily Scrum meetings the Scrum of Scrums should spend just 15 minutes addressing the following topics:
• What has your team done since the previous meeting?
• What is your team going to do before the next meeting?
• Any impediments facing your team?
• Are you about to create an impediment for another team?
The meeting should however be booked for longer than 15 minutes, typically 30 to 60 minutes in order to allow time for problem solving after all teams have provided their updates. Such problem solving discussions must only take place after the updates of the first 15 minutes have been completed.
There are no set rules about the frequency of Scrum of Scrum meetings. Their frequency should depend upon the degree of inter-team dependency, the size of the project and the level of complexity of the project. The greater these are, the more frequently the Scrum of Scrum should be held. However, 2-3 times a week is a good starting point recommended by experienced Scrum practitioners.
More information can be found here:
https://www.scrumalliance.org/community/articles/2007/may/advice-on-conducting-the-scrum-of-scrums-meeting