name background/security check after Citizenship interview

My hu*****and went to interview for US citizenship application yesterday. After
the interview, the officer wrote :" name background/security check" on a sheet.She gave the sheet to my hu*****and. I heard that few people get name background/security check after the interview of citizenship application.
Who also got name background/security check after the citizenship interviw?
How long will it take for name background/security check for citizenship application? Can you share the experience with me? Thank you!