Magnets are cool. There are all kinds of fun experiments you can do with them, but their usefulness can be rather...limited. A magnet is always a magnet. It always attracts. Sometimes you want that, such as with a fridge magnet, but not always. By using electromagnets, that all changes, and the applications become endless.
An electromagnet is a magnet that is created using an electric current, created by electricity. Since electricity can be turned on and off, so can an electromagnet. It can even be weakened or strengthened by decreasing or increasing the current.