An isochoric process is a thermodynamic process in which the volume of a system remains constant. During this process, any heat added to the system does not change its volume, leading to changes in pressure and temperature instead. This is often observed in rigid containers where the gas cannot expand or contract. In an isochoric process, the first law of thermodynamics applies, stating that the change in internal energy of the system equals the heat added to it. This means that if heat is supplied, the temperature of the gas will increase, while the volume stays the same, resulting in increased pressure according to Gay-Lussac's law.