What is the distribution rule in SAP B1?

When you create a profit center, the system automatically creates a distribution rule with the same name.
You can use Distribution rule for direct cost and revenues, which you can assign uniquely and in full to a specific profit center.
If you cannot define the total allocation. The system allocates any unassigned cost or revenues to center_Z profit center.

You cannot assign indirect cost and revenues directly to a profit center.