In this video, Estimation Theory is introduced in which unknown parameters are estimated from data, rather than assuming that problems can be described by fully known distributions or statistics. The taxi-cab problem from Topic 11 is highlighted as an example. Examples of parameter estimation problems are discussed, followed by the concept of an estimator. The concept of distinguishing point-estimators from an estimator as a random variable before a set of observations is introduced, and a numerical example of the sampling distribution of the sample mean is presented in depth.