The rules were created last year after the agency started classifying broadband as a utility like power or water, and required privacy rules more like home phone service. According to the FCC's official statement, your "sensitive information" includes: "precise geo-location, financial information, health information, children's information, social security numbers, web browsing history, app usage history and the content of communications." Information such as your email address or information about your internet service is considered non-sensitive and will still require you to officially opt-out. The rules also require ISPs to provide users with "clear, conspicuous and persistent notice" about the data they are collecting and to notify users in the event of a data breach.
As the New York Times notes, the decision will also hurt ISPs' ability to build out subscriber profiles that it can use to sell targeted ads. It will also limit things like the "new advertising options" that AT&T planned to explore with it's forthcoming purchase of Time Warner.