Abstract
Basic concepts are defined, such as what thermodynamics aims to, what a system is, which are the state functions that characterize it, what a process is.
Keywords: Adiabatic system, Boundaries, Classical thermodynamics, Classical mechanics, Closed system, Exchange of energy and matter, Heat transfer, Interactions, Isolated system, Macroscopic systems, Microscopic structure, Open system, Parcel, Processes, Quantum mechanics, Quantization of energy, State functions, Statistical mechanics, Surroundings, Thermal reservoir, Universe, Work.