What are the different types of computer processors used in all kind of computers?

When i looked at Dell computers i see intel celeron,and on other computers i see intel inside Pentium3,4,m e.t.c.So what are the differences and why do these companies use different processors

What are the different types of computer processors used in all kind of computers?norton antivirus 2007

The 2 biggest companys in the microprocessor market right now are AMD and Intel... heres a summary of each companys product lines:

intel:

Old processors: 286, 386, 486sx, 486dx, 486dx2, 486dx4

- These range from 0 to 100MHz and are very old and obsolete processors now. Some of them are still used in small embedded applications...

Pentium, Pentium 2, Pentium 3 and Pentium 4

- These were intels flagship processors, pentium 4 being the latest and most powerfull of them all.

Pentium D

- This is a Dual core model of the pentium 4 processor. It has 2 processing cores and is capable of performing 2 instructions simultaneously instead of just one.

Pentium M

- A mobile processor line designed for laptops and small computers.

Core, Core 2, Core 2 Duo

- This is intels latest offering. They are all based around a new lower power core so that they run with better performance and less heat dissipation. Less heat, means less cooling required. WHich means the PC doesn't consume as much power. The duo models are also dual-cored.