An EE application goes through the following stages as per the Immigration and Refugee Protection Act (the law under which an application is processed):
R10
Medicals - Bio metrics request (technically not a stage)
Criminality
Eligibility
Security
Here, the eligibility is the most crucial and time consuming stage. All your documents have to be evaluated , and seen if you meet the CRS and MEC you declared in your pre-ITA application. Only if your meet the CRS cutoff, is your eligibility passed.
Since this is a time consuming stage, involving lots of documents. The eligibility takes place in 2-3 stages. First a case analyst / assistant will review the documents and make a recommendation. Based on the recommendation the status of the eligibility will change to "Passed" / "Recommended passed" / "Met" or ""Review Required" or not met. Then the officer will review the recommendation and make the final determination.
In most cases, but not all, the first stage happens at Case Processing Center (CPC). The final determination happens at LVO.
The two most important stages of an application are R10 and eligibility. If you clear these you are 90% clear.
As soon as the eligibility is conclusively passed, i.e. by an officer, the security will start. For most applicants security is a straight forward 2-4 weeks game. But for some, if they get stuck in enhanced security screening, it may take up to a year.
To read more on stages, see
https://goo.gl/9si33j
To read on security, see
https://www.canadavisa.com/canada-immigration-discussion-board/threads/the-anatomy-of-a-background-check-in-depth-analysis.500146/
And for anything else, just ask.