Intergroups are service entities that focus exclusively on local needs (e.g. maintaining meeting lists) and are not part of A.A.’s larger decision-making/service structure. You’ll notice they don’t appear in the upside-down triangle. But there is a connection between the two as shown in the picture.
Though an intergroup falls within the broader definition of “general service” (service beyond the group level), it should not to be confused with “General Service”, shorthand for A.A.’s larger decision-making/service structure. Within SDI and many other places, Intergroups and General Service entities (Areas, Counties, Districts) coordinate with one another to divide up service responsibilities.
Further reading, please see our FAQ on the service structure of A.A..