Well first silicon is different than a lot of other elements.  It can be made into a semiconductor.  That means it can sometimes act as a conductor and other times act as an insulator.  Sometimes it can carry electrons, other times it does not. Silicon crystals are doped with other elements like phosphorous or boron arsenic which makes the silicon into a semiconductor.  It only takes a few atoms of phosphorus or boron to create a transistor.  Is that interesting?  Well think about a switch, like the one in your room to turn on and off the lights.  Silicon by itself needs some help to become a semiconductor.

Semiconductors can be used as little switches or transistors.  The average transistor in a computer is about 100 nanometers.  Soon it will be 65 nanometers and then perhaps even smaller.  How small is hard to say but probably not less than around 30 nanometers.  But that means that 3,000 will fit across a human hair.

The other thing about silicon is that it is a crystal.  So if you took a really powerful microscope and looked at the silicon atoms you would find out that they are all lined up in a perfect (well almost) pattern, like the ones shown above.  That is useful for a lot of things including making really small transistors.  If you think about it something that is only 100 nanometers wide is really only a couple of hundred atoms wide.  Crystals are valuable because if they are all lined up it is easier to make things with straight edges.  That is important because fabrication of nanometer scale transistors still uses a top down technique called photolithography. The other thing about crystals is that their properties are really consistent so from one nanometer to the next crystals will behave the same.

Image Source: Nature (SEM Photos of planar silicon photonic crystals)