This chapter discusses the properties of random variables. It expalins statistical properties of random variables like estimation of mean, variance, standard deviation, and higher order moments including skew and kurtosis with numerical examples. The chapter describes moment generating functions and characteristic functions used for finding higher order moments of a random variable and illustrates the use of these functions for finding moments numerical problems. It also explains energy and power signals. The chapter provides a description of how energy spectral density and power spectral density are estimated. It analyses use of correlogram and autocorrelation with examples. The chapter suggests that solved numerical examples are included to illustrate the concepts. The naturally occurring signals have some random component. These signals are random signals. The random variable can be discrete or continuous. A discrete random variable takes on the discrete values such as 1, 2, 3 etc.