Electromagnetism is one of the 4 fundamental forces of nature. Almost all the phenomenon we experience in our daily life is because of it (except for gravity). It creates 2 types of fields: electric fields and magnetic fields. Electromagnetism is when both fields are united. One example is a nail electromagnet. A nail is wrapped with a coil of wire and the wire is attached to an electricity supply. When you turn the switch on it becomes an electromagnet. Now the iron nail is magnetic so it will attract magnetic objects. But when you turn the switch off the magnetism of the iron nail goes away.