When current flows in a conductor, there will be a magnetic field due to flow of current. If current flows through a coil which are changing in nature (alternating current, called AC current) will create a magnetism inside the coil. This magnetism is due to inductive property of metal. If we stop current flow, this magnetism will not be destroyed completely. Will remain.
This is the property of a metal and varies conductor to conductor. Due to this magnetism there is a loss called inductive loss.