Allowing a handful of broadband carriers to determine what people see and do online would fundamentally undermine the features that have made the Internet such a success, and could permanently compromise the Internet as a platform for the free exchange of information, commerce, and ideas.

This quote is talking about the dangers of having a few internet companies deciding what people can do online. It explains that if this were to happen, it would pose a threat to the freedom that the internet offers for people to share information, participate in online commerce, and exchange ideas. Allowing a few companies to control the internet would result in a permanent change to the Internet and could damage the features that have made it so successful.