In this lecture we will begin with an important question: why bother with statistical thermodynamics? We will progress to basic statistical quantities and concepts such as averages, fluctuations and correlations and how to use them in practice to calculate the physical properties of systems. This will lead us to the determination of the true statistical error for system properties obtained by simulation. We will apply these ideas to commonly calculated properties such as diffusion, radial distribution functions and velocity autocorrelation, while also examining the physical meaning of these properties. We will conclude with a look at distribution functions: how they arise and what they mean.