SCI clearance stands for Sensitive Compartmented Information. It is a classification of intelligence information, sources and methods. All SCI is handled within a formal system of controls established by the Director of National Intelligence.
A level of security clearance is usually needed for national security and intelligence jobs in the federal government. Among the highest level is Top Secret, abbreviated TS. Additional clearances are required to work on certain highly sensitive programs known as Special Access Programs. The clearance level needed to work on these programs is typically known as TS/SCI. A person cannot apply for SCI clearance, they must be sponsored by a potential employer who wants to hire someone for a job that requires TS/SCI clearance.