Controlling Area and Company Code relationship in SAP?

A Controlling area can have the following 2 type of relationship with a
Company code
a. Single Company code relation
b. Cross Company code relation
This means that one single controlling area can be assigned to several
different company codes. Controlling can have a one is to one
relationship or a one is to many relationship with different company
codes.
Controlling Area is the umbrella under which all controlling activities of
Cost Center Accounting, Product Costing, Profit Center and Profitability
Analysis are stored.
In a similar way Company Codes is the umbrella for Finance activities.