They are codenames for processors (CPUs) or chipsets (a set of chips from which a motherboard can be manufactured). The codenames designate an individual architecture. I think I'd better give you a few examples, so you can understand the general idea.
<b>CPU Codenames</b>
P4:
-Willamette: P4s from 1.4 to 2.0Ghz, running 400Mhz FSB. Used 180nm technology.
-Northwood: P4s from 2.0 to 3.4Ghz, running either 400Mhz, 533Mhz FSB or 800Mhz FSB. 5-10% faster than Willamette. Some of them come with HT enabled; all of them have HT circuitry, some disabled. Uses 130nm technology.
-Prescott: Next generation of P4s, from 2.8Ghz to 4.xGhz. It's very likely that this generation of P4s has 64-bit circuitry, but as far as we all know, it will be initially disabled. Uses 90nm technology, and is the first commercial chip to do so. More information on it tomorrow; it is to be launched tomorrow.
Athlon XP
-Palomino: Initial Athlon XP, was available at 1.333Ghz to 1.733Ghz (1500+ to 2100+). Used 180nm technology and 266Mhz FSB.
-Thoroughbred A: Better core; better thermal protection. Still uses a 266Mhz FSB; it went all the way from 1.4Ghz to 1.8Ghz (1600+ to 2200+).
-Thoroughbred B, 266Mhz FSB: Enhanced core for clock scaling (extra layer of copper interconnects). From 1.4Ghz to 2.133Ghz (1600+ to 2600+)
-Thoroughbred B, 333Mhz FSB: Higher FSB is the only difference. Went all the way to 2800+ (2250Mhz).
-Barton (400Mhz FSB) - Higher FSB and better core, but somewhat slower clock speeds. Came in 2500, 2600, 2800, 3000 and 3200 flavors.
And there are also the chipsets... I'll just name Intel's, cause it looks a bit more organized.
<b>Chipset codenames</b>
-Springdale, i865 - Mainstream platform with support for 800Mhz and dual DDR400. Typical mobo: P4P800 from asus.
-Canterwood, i875 - State-of-the-art platform; identical to springdale, except for PAT (performance acceleration technology), which is supposed to boost speed by a few percentage points.
-(NEW - March 2004) Grantsdale, i915 - Mainstream platform for LGA775 (Intel's new socket) and prescott. Supports PCI-Express, a new PCI and AGP-replacement technology, and DDR-2, which enables higher memory bandwidth.
-(NEW - March 2004) Alderwood, i925X - State-of-the-art platform for prescott and LGA775 processors. Same as Grantsdale, except for PAT, again.
<font color=red><b>M</b></font color=red>ephistopheles