Computers use switches to represent information such as numbers and letters. These are more complicated than the switch you use to turn on a light. In fact, just representing a single number requires eight switches.
Mechanical switches are too slow and bulky to handle all the processing required to even do something as simple as write an email. To make computers work, inventors had to make a nonmechanical switch—a super-fast switch with no moving parts.
What was needed was a switch that could be turned on and off by electricity. This required finding a semiconductor, a naturally poor conductor that could be easily modified to conduct electricity under certain conditions.
The best material for the job turned out to be silicon, an abundant nonmetallic element. Using silicon as a poor conductor, the transistor was invented and the digital age became possible.