The material in which charges cannot easily move is called an insulator.

Here's why:

* Insulators have tightly bound electrons that are difficult to dislodge. This means that when an electric field is applied, the electrons don't flow easily, and the material resists the flow of current.

* Conductors have loosely bound electrons that can move freely. This allows for the easy flow of current when an electric field is applied.

Some common examples of insulators include:

* Rubber

* Glass

* Plastic

* Wood

* Air

Let me know if you'd like more information about insulators or conductors!