What to expect for both an ESI and a SPIN.
During an ESI, the investigator will cover every item on your clearance application and have you confirm the accuracy and completeness of the information. You will be asked about a few matters that are not on your application, such as the handling of protected information, susceptibility to blackmail, and sexual misconduct. You will be asked to provide details regarding any potential security/suitability issues.
During a SPIN, the investigator will only cover the security/suitability issue(s) that triggered the SPIN. The purpose of the SPIN is to afford the applicant the opportunity to refute or to confirm and provide details regarding the issue(s).