What is variance?

The variance of a random variable is a measure of its statistical dispersion, indicating how far from the expected value its values typically are (Wikipedia 2006). The variance of a real-valued random variable is its second central moment, and it also happens to be its second cumulant (Wikipedia 2006). The variance of a random variable is the square of its standard deviation (Wikipedia 2006).

Variance is the difference between what is expected and the actuals. it is the difference between "should take" and "did take". The deviation from the actuals is called variance. Variance can be of two types positive and negative.