What is Silicon Valley known for?

Explanation

Silicon Valley is the southern part of the San Francisco Bay Area in Northern California. 'Valley' refers to the Santa Clara Valley and 'Silicon' to the high concentration of companies involved in the computer industry. These have slowly taken over the fruit orchards that used to dominate the valley in the old days. Some of the hi-tech companies headquartered in the area are Adobe Systems, Apple, Google, Hewlett-Packard, Intel, Sun Microsystems and Logitech. The area has the highest concentration of billionaires in the US.