A computer is an electronic device that accepts data as input, processes data into information, stores information for future uses, and outputs the information whenever it is needed.
Computers, by a wider definition, have been around for thousands of years. One of the earliest computers was the abacus, series of beads arranged on metal rods. Beads could be slid back and forth to operate on numbers. This was a very rudimentary device and is not commonly thought of as a computer in modern times. Our idea of computers involves electricity and electronics.
Electricity makes computers much more efficient. The first computers used an incredible amount of electricity, which changed voltages in vacuum tubes to operate the computer. These computers were given instructions using punch cards, and were behemoths, taking up entire floors of buildings. Only the more privileged