There are three basic mechanisms for the transfer of heat between objects.

 

(http://www.spectrose.com/wp-content/uploads/2012/12/modes-of-heat-transfer-conduction-convection-and-radiation.jpg)

Conduction occurs when two objects are touching each other.  If the objects are at different temperatures, heat flows from the warmer object to the cooler one until they both are at the same temperature.

(<http://www.universetoday.com/82331/what-is-conduction/>.)

Convection occurs in a substrate (liquid or gas) when a warmer region of a substrate rises and meets a cooler region.  The cooler region then sinks and takes the place warmer region.

(http://kids.britannica.com/elementary/art-177312/When-water-is-heated-convection-causes-the-water-at-the)    

       

Radiation occurs when electromagnetic waves generated by an object are absorbed by another object.  If the absorption of energy of the object is greater than the release of energy than the object rises in temperature.  Unlike conduction and convection, radiation does not need a medium to occur.