The modern scientific name for heat is

Thermal energy is the part of the internal energy of a thermodynamic system in equilibrium that is proportional to its absolute temperature and is increased or decreased by energy transfer.

This is: physically, heat is understood as the energy that is transferred from one system to another or from one body to another, and this is a transfer linked to the movement of molecules, atoms and other particles.

In this context, it is important to keep in mind that bodies have no heat, bodies have internal energy. When a part of this energy is transferred from one system or body to another that is at a different temperature, we talk about heat.

So, the transfer of heat will occur until the two systems are placed at the same temperature and the so-called thermal equilibrium is reached.