Once upon a time when human realized that in a normal atmosphere its not possible to increase the CPU Clock speed above standard levels because of too much heat generated by CPU, Both Intel & AMD have hit the Clock speed boundary line. Heat is enemy of any processor and high 
clock speed means high heat and that means errors or “BOOM”. Desperate need of more speed ( faster processing) is the basic reason of why technology turned or shifted to Dual Core. So rather then increasing the clock speed of Processor it was decided to put two CPUs in One. That is what we call Two Cores or Dual Core. Nowadays Quad Cores (4 cores) and even Dual Quad Cores (8 Cores) are there in market.
clock speed means high heat and that means errors or “BOOM”. Desperate need of more speed ( faster processing) is the basic reason of why technology turned or shifted to Dual Core. So rather then increasing the clock speed of Processor it was decided to put two CPUs in One. That is what we call Two Cores or Dual Core. Nowadays Quad Cores (4 cores) and even Dual Quad Cores (8 Cores) are there in market. In a layman’s tongue here's an example. Let's say a single core (Pentium 4) is a two lane road with traffic running at 100kmph, and a Dual Core is a four lane road with a traffic running at 100kmph, and a Quad core is eight lanes running at 100kmph. All lanes (cores) are running at the same speed, but more lanes (cores) can pass a lot more traffic (Information or Data) than a single.
