Simply stated at whatisnetneutrality.org: "Net Neutrality is the principle that the company that connects you to the internet does not get to control what you do on the internet."
That principle protects one's freedom to communicate and to choose information sources, without being throttled or blocked by one's internet service provider (ISP). In this information age, that freedom becomes more-and-more widely recognized as a right. And it becomes more-and-more crucial for citizens of a constitutional democracy in keeping informed and active.
A like principle was in effect for the nation's telephone system. Our government deemed the telephone system a "common carrier" -- a public utility that must treat all messages (phone calls) equally, and not interfere with them. In the dial-up ISP days, that principle carried over to the internet, which then grew rapidly.
Later, big telephone and cable TV companies gathered most of the ISP market. And during the Bush II administration, the Federal Communications Commission (FCC) classified those ISPs as "information services," which are not common carriers.
Eager for the easy money to be had by just turning the valve to slow or speed data transmission, big telecoms lobbied against net neutrality. Courts struck down FCC tries at applying the net neutrality principle to ISPs classified as information services. An outcry -- including 4 million comments to the FCC -- came from the internet-using populace. And at last, in 2015, the FCC reclassified ISPs as "telecommunciation services", which are common carriers.
Now, having near-total control of our federal government, Republicans are acting to quash net neutrality and internet freedom. Already, Republican Congressmen and President Trump have repealed the privacy rule. No longer does an ISP have to get your explicit consent before it can use or disclose your browsing history, app usage or content of your messages. That repeal was done using the Congressional Review Act, and so was not subject to a Senate filibuster. Also, nine Republican Senators have introduced a bill to kill net neutrality and ban the FCC from ever adopting it again.
After the election, commissioner Ajit Pai seemed to relish his coming appointment as chairman of a Republican-majority FCC. "We need to fire up the weed whacker and remove those rules that are holding back investment, innovation, and job creation," he said. But Pai and the other Republican commissioner have taken the weed whacker to the flower garden. In spite of hundreds of thousands of new comments to the FCC in favor of keeping net neutrality, they have voted to hold a rulemaking session aimed at undoing its protections.