Reverse phone directories allow different phone number owners to find different types of information except those who deliberately blocked their number from displaying. Any redemption library will display a portion of the available information free of charge and charge a fee for more detailed information. The freely available data providers will be different. Generally, you can expect to pay without pay: phone type (cell, land line), area code, city, state, county, latitude, longitude, and area map (eg maps).
If you choose to purchase a paid subscription, you may find the following information: unpublished numbers, owner's name and details, and names and details of former owners. This is much more comprehensive data that can be useful in a situation where general information is not enough.
So are such libraries a tool from the "shadowy black hat" world? No, they do not. Reverse telephone directories are completely moral and legitimate, as long as their purpose is to validate the data, the status of the person and the address, and related personal goals. These services track all the searches they've made, which helps to prevent someone from being threatened. Such libraries can not be used by unscrupulous people who want to start harassing, disturbing or insulating someone or using their place and stalking a celebrity. All searches can be tracked for those who have done them to help prevent misuse.