A phone number starting with 855 is a toll-free number. As of 2014, toll-free numbers start with one of six codes: 800, 888, 855, 877, 844 or 866.
Toll-free calls are paid for by the party called, as opposed to the traditional method of the caller paying for the call. Toll-free numbers are regulated by the FCC and are primarily used for businesses. Oftentimes, businesses use toll-free vanity numbers, such as 1-800-Plumber, to make the phone number easier to remember for customers. The cost for the business providing the toll-free number is typically cheaper than long distance charges for the customer.