I was looking at Intel CPUs and I'm pretty new with all the computer stuff.
So I was hoping you could clarify me some things..
From what I understand, there are two "divisions" to Intel CPUs: Pentium and Celeron?
Is Pentium the lower version of Celeron?
So for every microarchitecture, (1st gen, Sandy Bridge, Ivy Bridge) there is pentium and Celeron?
What is Xeon then??
For every architecture for the last few years there has been a Celeron, Pentium, i3, i5, and i7. Xeons are CPUs built for servers and workstations. Celerons are a little bit lower end Pentiums, and Pentiums are essentially i3's without Hyper threading.
The naming conventions have been changing every year. So it is pretty much impossible to know the performance of a CPU (or socket compatibility) from the model number. The naming is a complete mess to be honest.
There are now about 2000 different models of x86 CPUs available. Far too many for anyone to remember all the details.
As Montosaurous says, the rough order is from worst to best is, Celeron, Pentium, i3, i5, and i7. But is easy to find example where an i3 is better than a i5, because they are from different generations or made for different markets.
For example the i3-3240 is better than a i5 760 and also better than a Core i5-2390T & i7-2655LE. A Celeron G555 is better than an i3-2312M.
But if you only look at chips from a single generation, ignore the low power variants, and don't consider AMD chips, then the rule is pretty much correct (for the moment).
Nevertheless, you really need to do some research before buying and not just look at the model numbers.
Nehalem is the 1st generation Core i3/i5/i7 CPUs, then comes Sandy Bridge and then Ivy Bridge. Haswell will be the 4th generation coming this June.
Nehalem is socket 1156. While Intel generally allows sockets to live for 2 generations socket 1156 was replace by socket 1155 which is used by Sandy Bridge and Ivy Bridge. Haswell will be socket 1150.
Intel has spent a lot of money marketing the Celeron (a.k.a. Celery) and Pentium names so they simply continue to use it. Celeron was always reserved for the weakest CPUs and still remains so. While the Pentium brand name was for Intel high end CPUs up until mid 2006, it has been relegated to the value segment when Intel released the Core 2 Duo / Quad series. The names didn't last long though since the Core i3/i5/i7 started selling in late 2008.
While the Core 2 Duo / Quad series brought back the performance crown to Intel back in mid 2006 those names are no longer used. Which is probably a good idea in a way... if Intel decided to keep using that nomenclature instead of the Core i3/i5/i7 I suppose they would need to extend the name further with the Core 2 Hex for Intel's high end "Extreme" CPUs.
Core i3/i5/i7 are generic enough you wouldn't know which ones are dual, quad and hex cores.