Conduction
Definition
Heat traveling through direct contact — molecule bumping into molecule, passing energy along.
Technical definition
Heat transfer through a material by microscopic collisions and electron motion, without bulk movement of the material. Fourier's law states the rate is proportional to the temperature gradient and the material's thermal conductivity.
Example
A metal spoon left in hot soup becomes too hot to hold — heat conducts up the handle atom by atom — while a wooden spoon stays cool because wood's thermal conductivity is hundreds of times lower.
Conduction needs contact; convection and radiation do not. Students often label all heat transfer 'conduction,' but the warmth you feel from a campfire on your face is radiation (no contact, travels through air), and the rising hot air above the flames is convection (bulk fluid motion). Touch the fire-warmed stones, though — that is conduction.