The INTEL Core i3 is the current generation dual core CPU. "Dual core" is a generic term used buy manufacturers to describe any CPU with two cores in them. Even some cellphones are advertised as having a "dual core" processor.
It all boils down to the architecture and how efficient they are at handling instructions. Newer CPUs are generally more efficient than older CPUs of the same family. Intel's current generation of Core i3, i5, and i7 "Sandy Bridge" CPUs (socket 1155) are on average about 10% faster than the older Core i3, i5, i7 "Clarkdale" CPUs (socket 1156) when clocked at the same speed.