The material that does not allow current to flow easily is called an insulator.

Here's why:

* Conductors: These materials have loosely bound electrons that can easily move, allowing electricity to flow through them. Examples include copper, silver, and gold.

* Insulators: These materials have tightly bound electrons that are difficult to move. This makes it very hard for electricity to flow through them. Examples include rubber, glass, and plastic.

Think of it like a crowded train:

* Conductor: Imagine a train with lots of empty seats. People (electrons) can move freely and easily through the train.

* Insulator: Now imagine a train completely packed with people. It's difficult for anyone to move, let alone change seats.

Let me know if you'd like to know more about conductors, insulators, or electrical conductivity!