Net Neutrality is the principle that all Internet traffic is to be treated equally by Internet Service Providers (ISPs), regardless of its origin or the protocol it uses. While Net Neutrality protections are in place, an ISP can not block, throttle, or prioritize traffic from specific websites or services (outside of performing nondiscriminatory traffic management and blocking illegal material). Abiding by these principles ensures that the Internet remains a level playing field for websites and services regardless of their relationships with individual ISPs.
The concept of Net Neutrality reflects how the Internet worked in its early days. Early ISPs provided their customers with a connection to the Internet and treated all data packets on their network equally from end to end. The content of the data packet did not matter — whether it was a webpage, email message, or an online game, a packet was just sent to its destination as fast and efficiently as possible. However, as the Internet matured and became more popular, ISPs began throttling or blocking certain types of traffic, like BitTorrent file transfers. Internet activists argued that discriminating against certain types of traffic limited innovation, leading to early attempts at Net Neutrality regulations in the 2000s.
Without those protections, an ISP could actively meddle in how their customers browse the Internet against their customer's wishes. An ISP could make side deals with specific websites to prioritize their traffic in a "fast lane," throttling the traffic of sites that don't pay. If the ISP also operated a video streaming service, they could prioritize their service over their competitors. They could also limit some types of traffic like VPN connections to only customers on a premium-priced Internet plan, or block certain traffic entirely.
Net Neutrality Around the World
The rules regarding Net Neutrality within a country are the responsibility of that country's regulatory agencies. These regulations have exemptions that allow ISPs to perform some traffic management, although the specifics of those exemptions vary widely from country to country. For example, ISPs may still apply some level of traffic shaping to maintain network performance by throttling certain types of traffic that would otherwise overwhelm a network.