If you connect an electrically neutral pith ball and a glass rod by a copper wire, you will find that the neutral pith ball has been charged similarly with the glass rod. This shows that charge has been imparted to the pith ball through the copper wire. Such materials like copper, aluminum, etc., which permit the flow of charge through them are called conductors of electric current.

On the other hand, if you connect the charged glass rod by a neutral nylon cord instead of copper wire, you will find the neutral pith ball will not be charged.