E&M stands for electromagnetics, which is the study of how fields and waves interact with the world.  In electromagnetics, the fields are no longer tethered to a circuit board and can instead move through space. Their interaction with the world around them (for example the human body or your cell phone or an aircraft) enables all kinds of imaging, communication, sensing and ranging applications. The ability of electromagnetic fields to carry power and signals enables wireless communication (like your cell phone) and wireless power transfer (for implantable medical devices, Airbuds, electric vehicles, and more).

Visible light, UV radiation, and infrared light are all forms of electromagnetic waves.  Optics is the science of bending and focusing light, which allows us to send signals and create images.  Such technology can be used to concentrate sunlight for solar cells or project blockbuster films on the big screen.