robert_deeni said:
In fact there are 3 kinds of checks on each applicant, which are the part of the process of PR. The visa processing office take a final decision only after successful completion of these procedures which are internally done and no one knows exactly when, how and where these checks are carried out. :-
Background check is done by visa post processing application with cooperation of visa posts where your education and experience credentials are from - this task verifies your claims and authenticity of documents.
Security check is done by Canadian intelligence and security agencies, with or without cooperation of proper authorities in countries you lived/stayed in, and it is done completely independently from CIC - CIC only gets result, which will be positive or negative, without any explanation (as it is classified). This task looks deep into your life, activities and associations to find out if you are/were involved or are/were associated in any way with anyone who is/was involved in espionage, terrorism, organized crime, radical movements, crimes against humanity, war crimes, etc..
Criminal check looks into your police certificates and verifies with relevant countries to see if you have a criminal record that may make you inadmissible to Canada.