
Project Unit Organization is a new concept in Oracle Fusion.It is a additional control provided by Oracle cloud.
For Oracle Fusion Instance access click here
If your organization is providing different kind of services and implementing project module,Project unit is used to control the project configuration based on the services.
There is no implementation option in Oracle Fusion and that is why Project unit plays a important role controlling some of the implementation option
They are operational subsets of an enterprise that conduct business operations using projects and need to enforce consistent project planning, management, analysis, and
reporting.

So as per above service type we need to create project units for them if we want to control the project,configuration,expenditures and revenue based on specific project unit
Project Unit and Business Unit Associations
You can create one to many and many to one relation between Project Unit and Business Unit.In other words you can associate one project unit with multiple business units. Conversely, you can
associate one business unit with multiple project units.

For the above example you can maintain independent setup data for each project Unit and sharing a single approach to financial management across all project Units as two project units are assigned to a single business unit
Alternatively, you can partition financial data using business units while sharing a single approach to project financial management across all business units by assigning a single Project Unit to all your Business unit

In above example -both China and USA Business Unit maintain a similar kind of consulting service and financial management process.So its ideal to assign a single Project Unit to these Business Unit to facilitate common project Financial management practice
Benefits
Supports role-based access control, ensuring users only see projects relevant to their unit.
Supports multi-national operations with unique financial requirements.
Enables standardization within business segments while supporting local compliance.
Facilitates accurate reporting by isolating financial activities to their relevant project units.
Watch here-how to create Project Unit in Oracle Fusion