Thermal Pastes

Thermal paste (also called thermal compound, thermal grease, thermal gel, heatsink compound, heatsink paste) is a thermally conductive (but usually also electrically insulating) chemical mixture commonly used as an interface between a heat source and a heating block or heatsinks of a 3D printer's hotend to improve heat dissipation/transfer.

The main task of thermal paste is to eliminate air gaps that act as thermal insulation from the interface area, in order to maximize heat transfer and dissipation.