Net Neutrality is the principle that an ISP should not restrict access to any legal content. For instance an ISP throttling bandwidth for connections to Google, but allowing full bandwidth access to Bing would be a violation of Net Neutrality It is discussed at length in this Wikipedia article.
The arguments for and against can seem somewhat arcane. Here is a graphic that shows what it might look like if the Telcos win their fight against Net Neutrality and impose a Cable TV like pricing structure.
[Gizmodo]
