Geothermal systems is a research concept and academic field investigating the natural processes involving the generation, transfer, and accumulation of heat from the Earth's interior within the crust. It examines the dynamics of heat sources (such as magmatic intrusions or radioactive decay), the characteristics and behaviour of permeable reservoir formations, and the movement and thermodynamic properties of circulating fluids (typically water or steam) that facilitate heat transport. The significance of this field lies in understanding Earth's thermal regime, assessing potential energy resources, and analyzing the interplay between thermal, hydrogeological, and lithological controls within specific geological settings.