Concepts

IAM user
A user is created in IAM to use cloud services. Each user has its own identity credentials (password and access keys).

The account name, username, and password will be required for API authentication.
Regions are geographic areas isolated from each other. Resources are region-specific and cannot be used across regions through internal network connections. For low network latency and quick resource access, select the nearest region.
AZs are physically isolated locations in a region, but are interconnected through an internal network for enhanced application availability.
Project
A project corresponds to a region. Projects group and isolate resources (including compute, storage, and network resources) across physical regions. Users can be granted permissions in a default project to access all resources in the region associated with the project. For more refined access control, create subprojects under a project and create resources in the subprojects. Users can then be assigned permissions to access only specific resources in the subprojects.

Figure 1 Project isolating model
Enterprise project
Enterprise projects group and manage resources across regions. Resources in enterprise projects are logically isolated. An enterprise project can contain resources of multiple regions, and resources can be added to or removed from enterprise projects.