A material which electrons do not travel through easily is called an insulator.

Here's why:

* Insulators have tightly bound electrons. These electrons are difficult to dislodge from their atoms, making it difficult for them to carry an electrical current.

* Conductors, on the other hand, have loosely bound electrons that can easily move, allowing for the flow of electricity.

Some common examples of insulators include:

* Rubber

* Glass

* Plastic

* Wood

* Air