Higher the number, theoretically the better battery consumption and performance

Hello Shanta, this is a very common source of confusion for virtually everyone looking at the iPhone 5. That's because of an unfortunate naming decision that Apple decided made.As I understand it, there's no current (new) phone on the market with a Cortex A6. And to my knowledge, know of NO device using it. The Cortex A7 came out last year and is designed for smaller, leaner phones. Some phones include both a Cortex-A7 and another beefier CPU. In this kind of design, the A7 handles light tasks and it switches over to a stronger CPU depending on workload. As with all the other CPUs, the Cortex A8 is designed to use the ARM v7 instruction set and is just a linear progression in capability in the Cortex series, so it's faster and scales better in response to workload. However, it is more a general use design than the A7, which is a specialized product.The confusion comes from Apple's own internal branding of CPUs , of which ALL are based on the ARM v7 instruction set. Apple's own internal terminology for their CPU on the iPhone 5 is "Apple A6", but that's only in reference to its "system on a chip" products, which meld both the graphics processor and the CPU onto the same chip. Specifically, the Apple A6 includes both a custom dual-core Cortex A9 and a graphics processor.So to recap, the common misunderstanding is that Apple uses a Cortex A6. It does not. Rather it uses a custom built Cortex-A9, which uses the ARM v7 instruction set (which is NOT a CPU, but rather a form of code) and Apple refers to this chipset as the Apple A6.The actual difference between the three kinds of processors that you are referring to is that the Cortex-A7 is designed to be energy efficient . Functionally, you would want a CPU to be dual purpose, both energy efficient and fast. The A8 is a good middle ground between efficiency and speed.The Cortex-A8 is designed to be faster . It is more of a general purpose design than the A7 or the A15 (not discussed here).The A6 must have been some kind of reference design, because it's not available even on the ARM website.Hope that clears things up. Please do ask questions if I've explained any bit of this poorly.

It basically means higher the model no. better the processor.Better in terms of clock speed,cores,battery consumption,better graphics and sometimes newer technology.A better processor also means you can install a better OS in the mobile phone.

The biggest the number , the newest the design of chip Architecture , which provides better Power / Consumption ratio . A8 for example clocks Higher and has more "HorsePower" with lower consumption in comparison with the previous models

i think main diffrence is in the clock speed and no of cores

Higher the number, theoretically the better battery consumption and performance

The most appropriate link for your query, check it out : http://www.arm.com/products/processors/cortex-a/index.php and click on the tab which says compare processors

Generally, the higher the number series, the better it is at processing data. Higher numbered chips are newer, thus having newer processing instruction sets and usually better power efficiency.