When two surfaces come in contact, the warmer surface gives up heat to the cooler surface as can be seen with a glowing burner on a stove heating the pot it is in contact with. In a building this is limited primarily to studs connecting outer and inner surfaces.
The movement of air as a result of air being warmed. Warm air rises seeking the coldest point. Convection is visible as wavy lines above a hot road. Convection is a major concern in the winter, but not in the summer.
Radiant energy travels in all directions seeking a cooler object to strike and then generates heat. Microwave ovens work on the same principles. Standard ovens heat the air, while a microwave heats what it sees. Infrared is like microwaves at lower frequencies. Most of us do not understand microwaves or electricity but we use and enjoy the benefits of them. We may not understand infrared radiation but we can learn to make it work for us by learning how to control it.