Domain

Primary identity of the organization
Linked to either a Google Workspace or Google Cloud Identity
An Google Workspace or Cloud Identity Account can only have one organization

Organization

Root node of the Google Cloud hierarchy of resources
Define settings, permissions and policies for all projects, folders, resources and Cloud Billing Accounts it parents

GCP Project & Folders

They are used to group similar resources together for easy management and tracking

Labels

Categorize and Filter resources using key value pairs
Great for cost tracking at a granular level