This picture shows a guy getting burned by the fire because he touched it. This is a form of conduction because the heat from the fire transferred to him and burned him through him directly touching the fire.
The transferring of heat energy through direct contact.
This picture shows a lava lamp. A lava lamp is a form of convection because the "lava" sinks to the bottom and rises due to the water heating up at the bottom and cooling down at the top causing it to sink.
The transferring of heat energy in liquids through the process of heating and cooling.
This picture shows a plate of spaghetti being heated in the microwave. This is a form of radiation because the heat in a microwave is moving in electromagnetic waves to reach a surface that will then absorb the heat or reradiate it.
The transferring of heat energy in the form of electromagnetic waves that the surface they hit absorbs.