The fundamental material used in making computer chips, it is a semiconductor, meaning it has electrical conductivity. Silicon is a chemical element: it is the most common metalloid, it is less reactive than its chemical analog carbon, it is the eighth most common element in the universe by mass, and it is the second most abundant element (after oxygen) in the Earth's crust. Silicon is the principal component of most semiconductor devices, most importantly integrated circuits or microchips. For an in-depth discussion as why it is widely used in semiconductors, visit the search link below!
Because silicon is an important element in semiconductors and high-tech devices, the high-tech region of Silicon Valley, California is named after this element, along with many other geographic locations with connections to the industry who also classify themselves as Siliconia.