Basicly, the government is trying to meddle in the net and allow isp providers to block or reroute your internet traffic.
Say your ISP is Evilnet (a spin-off of Starbucks), and you want to shop with my friend Shadowdragon. But MegaMart.com pays Evilnet to reroute traffic for all competitors in that product category to them, or at least make it a lot harder to get to competitors. Under what Congress is considering, that will be legal.
Here's one of my favorite online comics with another Net Neutrality strip.