What is the benefit of electromagnets compared to regular magnets?

An electromagnet is a core of magnetic material such as iron that is surrounded by a wire coil through which an electric current is passed to magnetize the core. When the current is turned off, the magnetic field disappears.

The main benefit of an electromagnet over a regular magnet is that the magnetic field can be easily and quickly changed through controlling the amount of electric current passing through the coiling

Thus electromagnets are used widely in electrical devices such as motors, generators, hard disks, loud speakers and MRI machines.