Processor Comparison Computer Processor Comparison?

Computer processor comparison? - processor comparison

I think buying a new computer for sale in the school. As one of the most important elements in determining the price and performance of a computer is used, the processor type, I wondered if someone could explain that the processor of superior quality and significance of the numbers:
Intel Pentium
Intel Pentium Dual-Core T____
Intel Core 2 Duo P____, T____

And so, enter the tracking number of T____ and P____, eg

Intel Pentium Processor T4200