Random Process, mean , variance, autocovariance, autocorrelation function. Random Walk model its mean, variance, autocovariance, autocorrelation function.
One of the easily understood and yet most significant time series model which used for forecasting/prediction purpose is the random walk model. This model undertakes that in every period of the variable picks a random step away from its past observation, and these steps are independently and identically distributed (i.i.d.).