so what is Core 2 duo?
its an intel technology which is intel core 2 duo which based on intel core microarchitecture

what really happens is
1.increase in delivering of instructions per clock cycle thereby decreasing exectuion time n increaing energy efficiency
2.more power efficient performance and more battery life for laptops
3.optimise the use of available data bandwidth
4.more efficient cache subsystem for these processors

read on for more info