Here is the "NXT intelligent blocks" of everyone familiar with. And this is the brain works in parts of the robot, who move the sensors and motors. (It should be noted, too long to write "NXT intelligent blocks" each time, "NXT" below.)

Here is a technical document called "LEGO MINDSTORMS NXT Hardware Developer Kit" has been published web site of Lego. (http://mindstorms.lego.com/) This is called "HDK" for short.
In this article are also circuit diagram of the NXT. You can decipher this, known about the mechanism of NXT,,,

,,, This is very difficult. I thought to introduce this going in order, too difficult even finely detailed. For the hard part, I would like to introduce as much as possible so roughly. If you are interested, please read the HDK further.

This is about the parts that make up the NXT.
The NXT contains 2 microcomputers. The reason why using 2 microcomputers, because one is not enough to process for that much volume.
Such as "boss and henchman" of these two microcomputers, one has to position always to instruction. This is called "main processor" which side to instruction and "sub-processor" with the side labeled. The sub-processor detect the amount of rotation of the motor, the detection of NXT button, and checking the voltage of the battery, otherwise the processing of the main processor is in charge.
The main side has been used "AT91SAM7S256" 32-bit microcomputer relatively upscale. If you buy this microcomputer, it is about 1,113 yen. (As of April 2009 at DIGI-KEY)
Then, I tried to enumerate the main microcomputer and IC is used to NXT. Fairly specialized information so you can skip.
Main processor: manufactured by Atmel "AT91SAM7S256"
Sub-processor: manufactured by Atmel "ATmega48V"
Motor driver IC: Sanyo "LB1836M" "LB1930M "
IC for serial communication: "ST485"
Bluetooth chip: manufactured by CRS "Bluecore"
IC for sound output: "SPY0030A"

So, what "microcomputer" as a part can be done at the first place?
Briefly, the microcomputer has the ability to calculate, can enter the signal, or output, or to store the information.
Features of the microcomputer are written in technical documents known as "data sheet".
For example, it is open to the public web site (http://www.atmel.com/) of a company called "Atmel" data sheet of "AT91SAM7S256" which is the main processor. However, this is written in English and that (more than 700 pages) information that is difficult to read too.