One of the fundamental forces in the Standard Model . Particles taking part in the electric interaction have to be electrically charged . They can either have a positive or a negative charge. Particles with the same charge repell each other while particles with opposite charges attract each other. This is due to the exchange particle of the electromagnetic force, the photon that travels between electrically charged particles.
The electromagnetic force is only medium strong, but it can reach very far. We can feel the effect of the electromagnetic force (for example as electricity), while it is impossible to feel a direct effect of the much stronger nuclear force . The Nuclear force can only reach for about the diameter of a neutron and the color force can reach even less far.
More about the virtual photon , the force carrier particle of the electromagnetic force on the main page.
About Electromagnetic Force in German. (elektromagnetische Kraft)