Just as people of different cultures use different languages, computers understand instructions in their own language. Computer convert all information into numbers, process it and convert it back to language that we understand. For this conversion they use a STANDARD CODING PROCEDURE called ASCII (pronounced askee) which stands for American Standard Code for Information Interchange. The standard allows different countries or different computer systems to exchange information easily.
Computers use the Binary system of numbers. Just as the decimal system has digits from 0 to 9 the binary system have only two digits 0 & 1. So All data put into computer is converted into combination of 0 &1.

Why 0's and 1's

Computer works on electricity and has circuits inside through which the current passes. The 0 signifies that there is no current in the circuit, while 1 says that there is current.