What is boolean algebra?

Boolean algebra is used to describe the output of electronic circuits that use only 0 or 1, i.e. binary. Such as And gates, Nand gates, Or gates and Nor gates. For example, an And gate might have two inputs, either one a 0 or 1. If both are 0 then the output is 0. If either is 1 and the other 0 then the output is 0. Only if both inputs are 1 is the out put a 1. Hence the name And gate, if the inputs are 1 and 1 then the output is 1. Wikipedia has an extensive article on Boolean algebra but it is a bit difficult to understand if you don't already have an idea of what Boolean is.