What is Microsoft GCC?

Microsoft 365 Government Community environment provides compliance with US government requirements for cloud services, including FedRAMP Moderate, and requirements for criminal justice and federal tax information systems (CJI and FTI data types).
In addition to enjoying the features and capabilities of Microsoft 365, organizations benefit from the following features that are unique to Microsoft 365 Government - GCC:
Your organization's customer content is logically segregated from customer content in the commercial Microsoft 365 services from Microsoft.
Your organization's customer content is stored within the United States.
Access to your organization's customer content is restricted to screened Microsoft personnel.
Microsoft 365 Government - GCC complies with certifications and accreditations that are required for US Public Sector customers. Microsoft GCC environment is largely equivalent to the Microsoft 365 Commercial environment, except that its data is segregated from commercial organizations. It can be configured, with appropriate licensing, to be 100% NIST 800-171 compliant. It leverages the Azure Commercial stack and is available from Cloud Solution Providers and through an Enterprise Agreement.

I hope this information will be helpful!
Tim Paine