If you are Australian, and over 40, you might remember this as a nostalgic catchphrase from the 80's and 90's, advertising motor oil made by Castrol.
While typically referred to as Oil, immersion cooling uses dielectric fluids to cool IT load - a non-corrosive, non-conductive liquid and either non-flammable or very high flashpoint, that has the viscosity of a mineral or baby oil.
Types of Immersion Cooling
Single-phase and two-phase immersion cooling are two different approaches to cooling electronic components by submerging them in liquid.
Every vendor has an explanation of the differences between the two, with useful infographics, however I like Submer's;
In single-phase immersion cooling, the liquid remains in a liquid state throughout the cooling process. The heat from the electronic components is transferred to the liquid through conduction. The liquid is then cooled by a heat exchanger or other cooling system.