Answer:
Conduction is a heat transfer mechanism. It is the dominant heat transfer mechanism in solids and it involves the vibration of the molecules of the solid. As heat is transfered to one end of the solid, the molecules at that end start to vibrate and in this process, collides with the adjacent molecules setting it to vibrate too. Also free electrons around the solid atoms (especially in metals) contribute to this heat flow. The continuous vibration is transfered from molecule to molecule gradually along the solid until the average kinetic energy (a measure of temperature) of the molecules along the metal has increased.
Convection is the dominant heat transfer mechanism in fluids, it involves the complete movement of the fluid molecule from a hot spot in the fluid to a cooler spot in the fluid. For convectional movement to occur, the molecules must first come in contact with the heat and absorb the heat first by conduction. As the heat increases, the fluid molecules break from just vibrating about a fixed point to moving completely to a cooler spot due to buoyant forces (due to the difference in density of hot and cooler fluid molecules). This clearly point out the fact that convectional heat transfer is first conduction, and then complete later flow of the fluid molecules.
