I'm sure centrino is a technology used in laptop world...
something about the CPU operating not 100% (which will be slightly slower) and using less power when not plugged to AC.... (something like that...) that way, the battery lasts longer...
but I never knew its not a chip....
well, prepare to learn something new again

You're actually in the same boat as most people I've talked to, or seen while in stores. Centino is NOT a technology either... its not a chip, a card, or anything physical at all. It is PURE MARKETING by Intel.
What you are thinking about is CPU throttling which has been in the laptop world for years. Older P3 laptops with SpeedStep did the same thing, among many many other laptops. All modern laptops will run at varying CPU speeds depending on processes to save battery life. It is not because of Centrino. My girlfriend's Dell 700m (non-Centrino) throttles from around 230mhz to 1.7ghz just like my Centrino HP laptop does.
The Centrino standard is based on 3 items: a Pentium M processor, a wireless card, and a motherboard chipset. Intel has a set standard of Centrino certified wireless cards and chipsets... if your laptop doesn't use a Pentium M AND certified chipsets and wireless cards, your laptop cannot be Centrino. Go buy a Dell laptop and you'll see that you have a choice of wireless cards. The second you choose a Dell wireless card instead of an Intel 2100 wireless card, your laptop is no longer Centrino.
Does that mean your battery life instantly gets cut in half? No.. it means you don't get that little Centrino sticker on your laptop. That's all.
And the best part of this whole thing is that the Centrino used to (and might even still, I'm not sure) not officially support 802.11g... only 802.11b, which is the slower standard. So there was a time when buying a Centrino laptop actually got you a SLOWER wireless chipset... it might even be the same case, but I believe Intel now has a Centrion G wireless card.
That's all Centrino is: a Pentium M and a chipset/wireless card that Intel believes will give you the best experience as far as wireless connectivity and battery life go.
And again, please let me make it clear that I LIKE CENTRINO. I recommend it and think a Centrino laptop is a better buy when compared to more desktop replacement style laptops. Just don't buy a laptop just because its Centrino... it's like buying a laptop because someone told you it was sprinkled with fairy dust... its meant to make you THINK its better even if it isn't always the case.