Infrared radiation refers to a type of electromagnetic radiation with longer wavelengths than visible light. It is not visible to the human eye, but can be detected as heat.
Wavelength refers to the distance between two consecutive peaks or troughs in a wave. Infrared radiation has longer wavelengths compared to visible light.
Heat transfer is the movement of thermal energy from one object or system to another due to a difference in temperature. Infrared radiation is involved in heat transfer processes.