The purpose of this book is to study the basic Principles and Propositions of Probability Theory - Distributions, which form the foundations of Statistics. An attempt was made to introduce the fundamental Principles for probabilities - distributions and to determine characteristic measures of random variables, with theoretical and numerical examples from economic and social life with detailed discussions and analytical explanations. It was deemed appropriate to include in the book Descriptive Statistics, which, among other things, helps the reader to understand certain basic concepts, such as statistical population, sample, variable, frequency distribution, etc., and to proceed on a more accessible path to perform data analysis. We have ensured that the proofs of Propositions and Examples are presented in the simplest possible way in the book, avoiding complex mathematical calculations. Additionally, there is an excel file with selected examples from the book.