The laptop processor is typically a lower-powered processor than those found in similar desktop machines, although some laptop makers have used desktop processors in their laptops to get a performance edge. Processors designed for mobile computing generally consume less power, and thus run cooler than desktop processors. This is important because you want your battery to last a long time and you also don’t want to burn a hole through your lap. Desktop PCs typically have massive heat-sinks and fans to cool them down, but it’s hard to fit that stuff into a tiny laptop, and fans drain laptop batteries quickly.

A useful term to understand is Thermal Design Power, or TDP. This indicates the maximum amount of wattage that the cooling solution for that processor will need to dissipate. It’s not like it will always dissipate that amount of wattage, but, generally, if you want a cooler processor, go for the lowest TDP you can get.

Performance characteristics that differentiate laptop CPUs include the amount of cores they contain, the cache memory, and bus speed–as well as the speed of the chip itself. Mainstream processors are moving toward containing dual cores. You can still get single core CPUs today, but there are performance benefits to dual-core, even if they are not huge. Cache memory is speedy local memory that allows the CPU to keep from accessing slower main memory as often, and bus speed determines how fast the processor talks to the rest of the computer. In addition to the raw processor performance characteristics, different cores have different abilities. To get a true understanding of performance you will have to look at specialized comparisons or benchmarks among different laptop models. This is often hard to do with laptops as it is not as easy to equalize other components in a test setup.

Words on Recommendations
If you want the best performance, Intel currently rules things with its Core 2 Duo processors; AMD is just not up to par. With that said, if you want a bargain, you may have to buy a laptop with an older Intel chip or an AMD chip. For laptop users performance usually isn’t the top concern. The CPU choice, however confusing (and it will be, certainly if you are looking to save some cash) may not really matter all that much unless you will be using your laptop as your primary machine and you are doing some multimedia or gaming on it. If so, stick with Intel’s Core 2 Due and go for the T7xxx series.

If you are looking to cheap out, or, to put it nicely, are more fiscally conservative, you will be faced with the prospect of going with AMD processors and/or outdated Intel chips that are not on Intel’s roadmap anymore. All of them will work fine, but you may not get the top-end performance that a Geek craves.