Here's a breakdown:

* Electromagnetic Spectrum: This spectrum encompasses all types of electromagnetic radiation, ordered by wavelength.

* Wavelength: The distance between two successive crests or troughs of a wave.

* Infrared (IR): Located just beyond the red end of the visible light spectrum. It has longer wavelengths than visible light but shorter wavelengths than microwaves.

So, while infrared rays are invisible to the human eye, they have a longer wavelength than the colors we can see.