A region in GCP a specific geographical location where you can run your resources. Each region has one or more zones; most regions have three or more zones. For example, the us-central1 region denotes a region in the Central United States that has zones us-central1-a, us-central1-b, us-central1-c, and us-central1-f. For further information please review GCP regions
We are now adding support in Dome9 to many more GCP regions. You can now reason about GCP entities specific to any region of your choice to create granular policies across your cloud environment.
The name of the regions in the Compliance Engine are also renamed to reflect the actual location name. This should not affect GSL, as it uses region Id.
The list of supported regions for GCP can be found here