The question "what is justice?", contained in the title of the book, is very old. It has occupied legal theorists and philosophers from antiquity to the present day. We could say that it is a question similar to the one Pontius Pilate addressed to Jesus Christ in the Praetorium: "What is truth?" However, the aim of this book is not to continue the search for an answer, which may not even exist. The author's purpose here is much simpler: it consists of the effort to bring law and legal science closer to the ordinary citizen; to take the law from the level of theory and bring it down to the reality of everyday life; to make it clear to the non-specialist what the rules of law mean and how they are applied every day in a multitude of issues (commercial, economic, family, inheritance, etc.) that arise from people living together in a community. Although law is directly and inextricably linked to human daily life, it does not attract the interest and trust of people to the same extent as other social and political sciences, such as history, sociology, philology, art history, etc. With the ambition to reverse this image, the author tries as simply as possible and with the use of many examples, to open for the non-lawyer a window into the "paradise" of legal concepts; to explain the functioning of many institutions; to simplify as much as possible legal constructs that seem difficult to understand; and to make it clear that the legislator, although sometimes (or in some eras) may overdo it in the production of laws (hence our well-known plethora of laws), generally does not act arbitrarily! Behind every legislative regulation lies the effort to solve everyday life problems and to resolve conflicting interests of society's members.