agilealliance.org/glossary/scrum-of-scrums/ displays the following:
A technique to scale Scrum up to large groups (over a dozen people), consisting of dividing the groups into Agile teams of 5-10. Each daily scrum within a sub-team ends by designating one member as "ambassador" to participate in a daily meeting with ambassadors from other teams, called the Scrum of Scrums.
Depending on the context, ambassadors may be technical contributors, or each team's Scrum Master, or even managers of each team.