Inside a wire there is a conductor like aluminium or copper which allows flow of electrons means current flows through it. And outside of conducting material is covered with insulating material like plastic, which is use for safety purpose.
Before electricity is passed through a wire it must have a source that is where emf comes along. EMF pushes the electricity through a conducting wire like copper or aluminimum that allows current to flow easily.
A wire contains mobile electrons as majority charge carriers and holes as minority charge carriers when an emf or potential diffrence is provided , electrons flow in opposite direction with holes(convection current flow)