This document provides an overview of key concepts related to normal distributions, including: 1) It introduces density curves and how they can be used to model distributions, with the normal distribution having a bell-shaped curve defined by a mean and standard deviation. 2) It explains how the mean and median can differ for skewed distributions and how they are the same for symmetric normal distributions. 3) It outlines the "68-95-99.7 rule" which indicates what percentage of observations fall within a certain number of standard deviations of the mean for a normal distribution. 4) It describes how data can be standardized using z-scores to transform it into a standard normal distribution for comparison purposes.