Electric ovens use heating elements to create heat. A heating element is a resistor---a material that resists the flow of electricity, turning it into heat. A lot of electricity flows into the heating element, heating it to red hot. A thermostat automatically turns the element off when the air in the oven gets above a certain temperature, and turn them back on again when the temperature drops too far.The entire oven is usually insulated to trap most of the heat.
In conventional ovens, the air inside sits fairly still since there is nothing to move it around and there is not enough room for air currents to form on their own. Some of the heat does flow through the air to the food by conduction--heat flowing from one molecule to the next when they bump into each other. Air isn't a very good conductor because the molecules are so far apart, so much of the cooking power actually comes from infrared radiation. Because the oven heating element is hot, it radiates intense infrared waves, and these are absorbed by the food and turned into heat. This infrared heat can be patchy and uneven, making it hard to get things to cook just right in older ovens.
Convection ovens make a very simple improvement on conventional ones: they add a fan inside. This fan circulates the air, bringing more heat directly to the food and cooking it more evenly. Convection ovens also cook the food more quickly than conventional ovens. A dish may require a lower temperature and a shorter cooking time in a convection oven than it does in a conventional one.
Other Electric Oven Features
Most electric ovens have a grill shelf. This shelf is directly below a row of heating elements. When the broil setting is turned on, these heaters are turned on full blast while everything else is left off. This intense heat caramelises the food by heating up the sugars in the surface like a grill does, making it a good indoor substitute for grilling. Many electric ovens now also have a wet heat feature. Hot air can absorb a lot of water, so ovens tend to dry up the food by making water evaporate out of it. Wet heat ovens blow water through a fan into the oven to increase the humidity, which stops moisture from evaporating out of the food. This keeps everything moist and tender.