Hi Mohammad,
We have many threads discussed on the same issue. Search twice before raise an issue on forums. It leads to duplication of data and inferior quality of content with multiple answers.
1. In simple terms, Cost Center and Internal Orders both are cost object objects i.e. which collect costs against it.
2.The difference is CC is a permanent record in the system where as IO is used for a temporary purpose (for marketing cost or trade fairs cost to be tracked) and settled later to a CC or COPA area.
3. You can't have budgeting control on CC and the same is available in IO.
Also, both have their own pros and cons.
Go through the below threads to understand better.
cost center and Internal Order
Cost Center and Internal Order Budgeting
Diff between, Cost Centre, WBS Element and internal Order
BR, Srinivas Salpala