In physics, thermal conductivity, k (also denoted as λ or κ), is the property of a material's ability to conduct heat. It appears primarily in Fourier's Law for heat conduction.
Heat transfer across materials of high thermal conductivity occurs at a higher rate than across materials of low thermal conductivity. Correspondingly materials of high thermal conductivity are widely used in heat sink applications and materials of low thermal conductivity are used as thermal insulation. Thermal conductivity of materials is temperature dependent. The reciprocal of thermal conductivity is thermal resistivity.
Read more about Thermal Conductivity: Units of Thermal Conductivity, Measurement, Experimental Values, Definitions, Physical Origins, Equations, Simple Kinetic Picture