Thermal Energy is transferred in three ways:
As you can see, the pan holding the soup is extremely hot because the stove is hot. The bowl is touching the hot stove and the heat is transferred to the bowl, to the soup. So if you touch it, it will be very hot.
The picture is showing the pressure cooker has water that is being heated up by the flames underneath it. At first the water is all the same temperature, but gradually the water at the bottom is being heated up. Since hot water is less dense than cold water, the hot water goes up while the cold water is going down. Then, when the cold water is closer to the flames, it heats up and goes to the top. This keeps going in a continuous cycle until it is all the same temperature. This can also apply to air as well.
The candles are radiating heat because the heat from the fire is going outwards, spreading/transferring more heat.
The Solar Oven my group and I made, successfully went over 150 degrees Fahrenheit, to melt some cheese on a quesadilla we made. We had newspaper on the sides for insulation, tin foil everywhere to reflect the sun in the direction of the cheese. We had black paper on the bottom of the shoebox to absorb heat, and plastic wrap to cover the place where the quesadilla would be, so no heat got out.