A code which consists entirely of 2 numbers or states, represented as 0 and 1. Can be used as a base-2 counting system.
Binary has place values that work on powers of 2 instead of powers of 10 as in our normal decimal system.
So a binary number like 1101 is (1*1)+(0*2)+(1*4)+(1*8) = 13.
If you care to learn things like Binary Addition, see 
http://www.learnbinary.com/
One page links to BinaryCode:
