What are the Differences Between Intel Pentium D, Core Duo, Dual 2 Core and Pentium Dual Core?

Difference between Intel Dual Core VS Core 2 Duo
Which one is Fast & Better Performer Intel Pentium D VS Core 2 Duo VS Dual Core
Comparison between Dual Core VS Core 2 Duo in simple language.
Confused about the difference between Pentium D vsDual Core vs Core Duo vs Core 2Duo ? Well here is the explanation.
First of all, let me tell you that Dual Core is a name of "class" or architecture of processors which refers to any processor (weather its Intel or AMD) with two cores on the same chip. Whereas Intel Core or Intel Core2Duo is a registered trademark [™] of the Intel Corporation. Many peoples, evengeeks sometimes gets confusion between Core 2 Duo & Dual Core or Dual Core & Core Duo. The fact is all the above mentioned processors are Dual Core processors.
What is Dual Core Architecture:
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 andthat 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.
Dual core technology refers to two individual microprocessors on a single die cast chip.

This is essentially two processing units (CPUs) in one. The advantage of a dual core chip is that tasks can be carried out in parallel streams, decreasing processing time.
Now lets see the difference & Compare all of them line by line as per their release sequence. Intel has, several dual core processors mentioned below.
1. Intel Pentium D:
The early model for desktops. CPU comprised two dies, each containing a single core  residing next to each other on a multi chip module.

Pentium D is slower than any one of the below, It consumes higher power and so it gives more heat and even its not good in terms of Over Clocking.
2. Intel Core Duo:
The Core brand refers to Intel’s 32-bit mobile dual-core x86 CPUs that derived from  the Pentium M branded processors.

The Core brand comprised two branches: Duo (dual-core) and Solo (Duo with one disabled core, which replaced the Pentium M brand of single-core mobile processor). Core Duo was Intel's first dual-core CPU for laptops. It's a whole new architecture, using two cores on a single die, which simply, gives you two chips in one package. Running at lower speeds than the old Pentium line.
The Core Duo conserves substantial power & racketing up clock speed while offering what was, at the time, record-breaking performance.
3. Intel Core 2 Duo:
The Core 2 brand refers to a range of Intel's consumer 64-bit x86-64 Single, Dual  and Quad Core CPUs based on the Intel Core micro architecture.

The single and Dual Core models are single die, whereas the Quad Core models comprise of two dies, each containing two cores, packaged in a multi-chip module.
Core 2 Duo processors are much popular these days, It has more powerful Dual Core chip, The best performer, It consumes less power in comparison to any of the above mentioned CPU. No over heating issues, it runs cool and a perfect Over Clocker. Once“I” overclocked my Core 2 Duo E6750 (2.66Ghz)  to 4 Ghz on airwith Sunbeam Core Contact Freezer. System was completely stable and temps were awesome.
4. Intel Pentium Dual Core:
The Pentium Dual Core, which we found to be an excellence choice for overclockers on a low budget, is based on the popular Core 2 architecture.

In fact, the processor cores are  the same, but the CPU comes with only 1 MB L2 cache instead of 2 MB or even 4 MB. In addition, some features, such as Intel's Virtualization Technology (VT) are disabled. The result is a castrated Core 2 Duo processor, using the small cache size and limited to 1.6 to 2.0 GHz clock speed at FSB 800 system speed.
Intel Pentium Dual Core are based on either the 32-bit Yonah (T2060, T2080, and T2130for notebooks with 1mb L2 cache) or 64-bit Allendale (E2140,E2160 and E2180 for desktops with 1mb L2 cache)
Later on Aug 2008, the 45nm E5200 Wolfdale Launched for mobile or desktop computers with larger 2mb L2 cache and 2.5Ghz clock speed. This model is highly suggested in terms of over clocking. The best over clocker in such cheap price, with some enthusiasts reaching over 6GHz clock speed using Liquid Nitrogen cooling.
Intel Dual Core processors are downgraded version of Core 2 Duo, less expensive with smaller cache, but still very adequate for general mainstream computer use. In terms of performance its more or less equal to Core 2 Duos. Intel launched it with very low cost to grab the lower end market. Intel Pentium Dual Core Processors are less power consumer (65W) in comparison of Pentium D (130W). Though it has a smaller L2 cache, it has proven to be much faster than the Pentium D under the test of CPU hungry applications.