Heat is a way of sharing energy. Heat is shared by conduction, radiation and convection.

Conduction is when something that is hot touches something that is colder and shares its heat. Heat always moves from something that is hot (and has more energy) to something that is cold (and has less energy).

Radiation is when something shares heat by sending it as waves. The Sun does this, as does a radiator heater in a room. Radiation waves can go through space, which is why we get the Sun's heat.

Convection is the way that heat can be shared through gases like the air and liquids like water. Hot gases and liquids rises. When they rise, they push colder gas or liquid out of the way. This starts up a circulating movement. The whole ocean currents of the Earth do this.

The difference between a convector heater and a radiator is this: a convector heater is designed to make warm air rise and so usually is made like a tube filled with heating wires. The outside is usually cold. A radiator is designed to send out heat waves and is often solid, and its surface is hot. An electric bar fire is a good example.

Many heaters do both of these things. In the video below you can see how heat can change the nature of many materials, in this case food. In fact, it can change them too much, which is why we often need to control either the temperature of an appliance, or the length of time it is on.