There are three ways that heat can travel from one place to another: conduction, convection and radiation.
CONDUCTION: This is the method that heat travels through a solid. Liquids (apart from mercury) and gases are very poor conductors of heat.
In a solid, the atoms are vibrating in fixed positions. If one end of a metal bar is heated then the atoms vibrate with increased frequency and amplitude. This causes the neighbouring atoms to vibrate faster and so on. In this way heat energy is transferred through the material. Note that the atoms stay in their positions.
All metals are good conductors of heat. Non-metals are poor conductors (insulators) of heat.
CONVECTION: If a liquid or gas is heated the atoms move further apart and so the liquid or gas expands. This causes its density to decrease and so is less than the surrounding (cooler) liquid/gas. This causes the warm liquid or gas to rise. Cooler denser liquid/gas then moves across to take its place. This in turn is heated, expands, becomes less dense and rises. In this way a current, called a convection current is set up in the liquid/gas and eventually all the liquid/gas is heated.
Note that, unlike conduction in a solid, the atoms do move and exchange positions with other atoms.
(THERMAL) RADIATION: Both conduction and convection require a medium for heat to travel through.
The Earth gets most of its heat from the Sun. Since there is no medium between the Earth and the Sun there must be another method that heat can be transferred. This method is called (thermal) radiation.
Any hot body will emit em radiation called infra-red waves. It is by this process that heat energy can travel through a vacuum (or through a medium).
Dark objects are good absorbers/emitters of infra-red waves.
Light white objects are poor absorbers/emitters of infra-red waves.
Shiny objects are good reflectors of infra-red waves.
[NOTE: do NOT confuse thermal radiation with nuclear radiation].