Net-Neutrality, in a simple description, is a law in place that prevents an ISP from restricting or throttling connections to websites based on how much someone is willing to pay.
Net-Neutrality is the only thing keeping your internet experience equal and unrestricted. Currently, the only restriction on your internet is which internet package you buy, though this only affects your overall internet speed and bandwidth. Imagine a world where Internet Service Providers (i.e. Charter, Frontier, Time Warner Cable, etc.) force you to pay extra in order to access certain websites. Where not every website is accessable with a standard internet package. A world in which your ISP will throttle your connection to websites unless you pay more for a "fast-lane package".
This is a world without Net-Neutrality.