To be honest, there is no such thing. The term “four cores” has been abused for decades and has been accepted for generations. One reason is that few people know how heat sinks work, and even fewer people know how they are made.
The term "core" is used to describe the assembly of components. The assembly includes tubes, fins, headers and side panels. All of these components are brazed together to create the core. The radiator core can be made from several different configurations and materials. It can be made of copper or aluminum and each layer consists of a set of tubes and fins. The number of tubes in each layer can vary depending on the material and application. In this case, the term "four" refers to the number of tubes in each layer.
This image is what most people call a quad core. In fact, there is only one core in the photo. They refer to the number of "tubes" in each layer. The correct term used by most radiator professionals is "four rows", which refers to the number of tubes. The copper heat sink is outdated and replaced by aluminum.
Aluminum radiators are more confusing due to changes in design concepts. The tubes in aluminum radiators tend to be much wider than the old copper ones. This provides more dead space between the contact surface and the smaller tube. The height of the fins in the aluminum heat sink is also much shorter, which will create more layers in the same given space. As a result, an aluminum heat sink with two rows will dissipate heat beyond a four-row copper heat sink.
This radiator uses two rows of 1 inch wide aluminum tubes. All aluminum cores are furnace brazed and they are 100% aluminum. This eliminates the insulating effect of solder (lead) in the old copper unit.
A multi-slot plate that is suitable for all tubes is a "cart". Vertical to the title is the side panel or end panel. It is the collection of two headers, fins, side plates and tubes that make up the core. Therefore, the correct term for the aluminum heat sink shown above is "two rows", which is superior to four rows of copper units.