What does IMM UCI 5257 in the Canadian tourist visa form mean?

UCI is the abbreviation of unique customer identifier. It represents the unique identification number of the applicant. If the applicant submits any application to Immigration Canada for the first time, its electronic system will give the applicant an identification number, and all subsequent information and applications of the applicant will be associated with this UCI. This number can be found in the circular letter, work permit, study permit, maple leaf card and other documents of the Immigration Bureau.