Final answer:
A conductor is a material that permits a large number of free electrons to move through it, such as metals and salty water due to their free ions. Superconductors can conduct without energy loss, compared to insulators like plastic and glass, which do not allow easy movement of electrons.
Step-by-step explanation:
The material that permits a large number of free electrons to move through it is known as a conductor. Materials like metals have a lot of free electrons that are not tightly bound to their atoms, which allows them to move relatively freely and thus conduct electricity. Furthermore, substances like salty water, with their free ions, also facilitate the movement of electrical charge.
Superconductors are a special class of conductors that allow the movement of charge without any loss of energy. On the other hand, materials that hold their electrons more tightly are called insulators; these don't permit easy movement of electrons and include plastics, glass, and wood.
Resistivity is an important measure in this context, quantifying how difficult it is for charge to move through a material. It highlights the significant difference in conducting abilities between conductors, semiconductors, and insulators.