Thursday, February 26, 2015, was a good day for internet freedom campaigners in the United States. On that day, the Federal Communications Commission (FCC) in the US voted to more strictly regulate internet service providers (ISPs) and to enshrine the principles of “net neutrality” as law.

The vote reclassified wireless and fixed-line broadband service providers as Title II “common carriers”, a public utility-type designation that gives the FCC the ability to set rates, open up access to competitors and more closely regulate the industry. “The internet is the most powerful and pervasive platform on the planet,” said FCC chairman Tom Wheeler. “It’s simply too important to be left without rules and without a referee on the field.”

Two years on and US President Donald Trump’s new FCC chairman, Ajit Pai, a former Verizon lawyer, has announced plans to overturn the 2015 order, in turn gutting net neutrality. A vote on this proposal is due to take place on May 18. Here’s why it matters.

n What is net neutrality?

Net neutrality is the idea that internet service providers (ISPs) treat everyone’s data equally, whether that’s an email from your mum, a bank transfer, or a streamed episode of The Handmaid’s Tale. It means that ISPs don’t get to choose which data is sent more quickly and which sites get blocked or throttled (for example slowing the delivery of a TV show because it’s streamed by a video company that competes with a subsidiary of the ISP) and who has to pay extra. For this reason some have described net neutrality as the “first amendment of the internet”.

n What is the difference between an ISP and a content provider?

ISPs provide you with access to the internet and include companies such as Verizon, Comcast, Charter, CenturyLink and Cox. Content companies include Netflix, Hulu and Amazon. In some cases, ISPs are also content providers, for example Comcast owns NBCUniversal and delivers TV shows through its Xfinity internet service.

n Who supports net neutrality?

Content providers including Netflix, Apple and Google. They argue that people are already paying for connectivity and so deserve access to a quality experience. Mozilla, the non-profit company behind the Firefox web browser, is a vocal supporter, and argues that it allows for creativity, innovation and economic growth.

More than 800 startups, investors and other people and organisations sent a letter to Pai, stating that “without net neutrality, the incumbents who provide access to the internet would be able to pick winners or losers in the market. They could impede traffic from our services in order to favour their own services or established competitors. Or they could impose new tolls on us, inhibiting consumer choice.”

Many consumers support the rules to protect the openness of the internet. Some of them may have been swayed by Last Week Tonight host John Oliver, who pointed out that restrictions are important.

Who doesn’t support the FCC’s 2015 net neutrality rules?

Big broadband companies including AT&T, Comcast, Verizon and Cox. They argue that the rules are too heavy-handed and will stifle innovation and investment in infrastructure and have filed a series of lawsuits challenging the FCC’s authority to impose net neutrality rules.

Publicly, however, the message is different. Verizon released an odd video on the topic, insisting that they were not trying to kill net neutrality rules and that pro-net neutrality groups are using the issue to fundraise. Comcast also launched a Twitter campaign insisting it supports net neutrality.

n Are there other reasons why people don’t like the 2015 rules?

Yes. Opponents don’t like the idea of putting the federal government at the centre of the internet when, as Pai has said , “nothing is broken”.

The new FCC chairman argues that the 2015 rules were established on “hypothetical harms and hysterical prophecies of doom” and that they are generally bad for business. “It’s basic economics. The more heavily you regulate something, the less of it you’re likely to get,” he said.

The big broadband companies publicly state they are quibbling the Title II “common carrier” designation rather than net neutrality per se. They believe they shouldn’t be regulated in the same way that telecommunications services are and prefer the light touch regulation they would otherwise be subject to under their previous Title I designation of the Telecommunications Act of 1996. The FCC lacks the direct authority to regulate Title I “information services”.

n How does this tie in to Trump’s approach to the internet?

Trump’s Republican party is showing its colours as friendly to big corporations, even if it leads to the unfettered accumulation of corporate power. It’s the second major roll-back of Obama-era internet protections. In March, Congress voted to allow ISPs to sell the browsing habits of their customers to advertisers. The move, which critics charge will fundamentally undermine consumer privacy in the US, overturned rules drawn up by the FCC that would have given people more control over their personal data. Without the rules, ISPs don’t have to get people’s consent before selling their data — including their browsing histories — to advertisers and others.

n What can people do?

There are 10 days to protest the roll-back of the FCC’s net neutrality rules. You can write to the FCC and Congress or leave a voice message for Mozilla, which will collect them all together as an audio file and send them to the FCC.

— Guardian News & Media Ltd

Olivia Solon is a senior technology reporter for Guardian US in San Francisco.