Specialty consumer reporting agencies collect and share information about your history including housing, employment, medical and banking records. This article from the Consumer Protection Financial Bureau breaks it down into more detail. From the article:

Reports may be compiled for your history of:

• Opening or using bank accounts (including writing or bouncing checks or overdrafts)
• Apartment rental payments
• Car insurance claims
• Homeowners and renters insurance claims
• Payday lending
• Utility payments
• Phone bill payments
• Employment
• Medical records or payments

You might not know these reports exist unless you run into a problem, such as not getting a job, lease, insurance, or checking account, or when a utility company asks you to put down a deposit before starting service with you.

Just like with the big three consumer reporting agencies, you can get free copies of your reports every 12 months from many of the specialty consumer reporting agencies. Other specialty consumer reporting agencies may be able to charge you a fee for your report. Keep in mind that not every agency will have information on everyone. You have to request the reports individually from each agency.