Intel® Centrino is on the verge of entering generation 3. The first, which took the market by storm, was based on the extremely popular Dothan core and the i855GM/PM chipsets. Generation two took over with PCI-Express, DDR2, faster bus and an updated core, but now it is time for generation 3 and this time we get access to dual cores with the new Yonah circuit. As we have earlier reported Intel has chosen to use a, the least to say, confusing PR-rating: The first letter marks the power consumption of the processor: T stands for 25-49W, L 15-24W and U <14W. The following four digits indicate in order: number of cores (1 or 2), the computing power (the higher the better) and the last two is a bit uncertain but are at the moment just two zeros. They may very well have an important task to fill later on, with updates and such.
Full Article: NordicHardware
Matbe also have good article, and already "babeled" here