Pretexting occurs when a thief has done prior research on your personal information, and uses this information to bait you to release more sensitive information, such as a credit card number or Social Security Number.
The schemer will call you on the telephone, and lead you to believe they are a business that requires this information. Most people tend to believe them, since they have their name, address, and telephone number.
Ref.: http://www.utica.edu/academic/institutes/cimip/idcrimes/schemes.cfm