You are talking about the R10 completeness check. It is done when they start processing your application and just before updating the results of your medical examination. The actual review of eligibility starts right after criminality. Criminality is where they check your police clearance certificate and run your name on their system to look for criminal records - if they find something, they will ask you to get RCMP clearance as well. After this, they will do a security check which could take from a few days to several months depending upon how fast they can confirm you are not a threat to Canada.