EMF is a physical field produced by electrically charged objects. It affects the behavior of the objects in its vicinity. The closer you are to the source of the field, the higher the intensity of the magnetic field. You can't see, hear or feel the EMF. But it surrounds us everywhere. The earth creates its own magnetic field and some other natural sources, but also different human-made electronic devices such as computers, tablets, mobile phones, radios, home appliances etc.