Hi,
Cost center is a responsible center in SAP. It cannot be
defined as statistical but in transactions it may become as
per other co objects.You will be able to find out the
performance of the cost center using activities and plan
values with actual value. This is lowest cost object in SAP.
This will become a statistical object when you allocate the
cost to other higher objects. Cost can be allocated to other
cost centers or co objects but not fi objects like
GL,assets, inventory etc. can be defaulted in transactions
through cost element. It cannot be a cost object for a
revenue element, revenues are always taken for other higher
CO objects. No budget functionality is available but
planning functionality is available and is always measured
for a year in business.

Internal order is the second CO object - which can be
defined as statistical or real. You will be able to define
Budget and planning figures - more than one year also. Can
control the postings of FI through budget controls. You can
have the report of Plan vs actual including commitment. Cost
cannot be allocated but settled through settlement rules and
profiles. The receiver of the values can be any object not
like Cost center - can be CO objects and FI objects. Ideal
for R&D expenses capitalisations, etc. Status profile is
linked to this which controls many individual transactions
in each status which is a part of this Internal order. It
can also receive postings of activities from Cost center.
Settlement profile is an wonderful tool for variety of
settlement - needed for FI and CO - legal requirements also
and Revenue requirements also for any country.

All SAP CO orders like Production order, Plant maintenance
order, etc will behave like Internal order with more
functionalities.

Thank You.