Central vs Central Services instance definition

Hello,

We are installing a new ECC 6 and Netweaver 2004s ABAP+Java system. We intend to run the central services instances (ASCS and SCS) on the database server. In this case, do we still have a central instance? My understanding is that the central instance is where the enqueue and message server are running. If we still have a central instance, what makes the central instance different from any other application server instance in our environment?

Thank you, George Barta