This chapter presents basic information about the nature and essence of the enterprise. The first subchapter shows both the well-known and less popular definitions of an enterprise and an industrial enterprise. They have been shown through the prism of various approaches, including definitions from various countries. The second part discusses the features of an industrial enterprise, with particular emphasis on: organizational separateness, economic separateness, legal separateness (legal personality), territorial separateness and technical and production separateness. The next part focuses on the goals and tasks of an industrial enterprise, with particular emphasis on the way they are formulated. Both strategic, tactical and operational goals were discussed. The subject of the considerations in the fourth part were the functions of an industrial enterprise, including a detailed description of the production, technical, organizational and personnel functions. The division of enterprises according to various criteria is presented in the next section. It focuses on such criteria as business profile, the size of the enterprise, form of ownership, production type, type of production process and market legal form. The last part discusses the market on which an industrial enterprise operates. Its features were presented, as well as the type of industrial products, types of customers and differences between industrial and consumer marketing. Particular attention was also paid to OEM (Original Equipment Manufacturer) and MRO (Maintenance Repair and Overhaul).