What is Net neutrality?

Today, many people who are in the world can use Internet.
However, we have some gap between countries or people. Different amount when people access into Internet is biggest issue and it has discussed. Mostly, users pay money for provider. But this amount is not same in the world. For example, government pays in some countries so citizens can use Internet by free, in contrast, some countries like Japan, people pay expensive money for provider per month or year. It is not neutrality. It happens not only in the computer world but also telephone. Many telephone companies come up with different amount or merits.

Ahaaaaaaa~, it is really hard topic to me, so I couldn’t understand what “Net neutrality” is exactly. I’m lost!!