The default response
The built-in response that makes sure someone is always alerted.
Every organization has one built-in response, labeled Default. It always does the same thing: notify the team that owns the monitor when an incident opens. That is what makes sure a new monitor alerts someone without any setup.
Because it is the safety net, it is locked. You can turn it off, and you can choose which kinds of incident it covers, but you cannot rename it or change its action. To do something different, create a new response, or choose Duplicate to start from a copy.