From the Link : http://www.cic.gc.ca/english/helpcentre/answer.asp?q=022&t=4
What happens after I send in my application?
Once you have sent your application, the steps to process it vary depending on the program for which you applied. However, here are the main steps:
Immigration Application Processing
Screening of the Application
•Once your application is determined eligible your application will be assessed by a CIC officer.
•An application may be returned or refused if ◦you are ineligible to apply;
◦the application is incomplete; or
◦the answer to a question is not detailed enough.
•To avoid your application being returned, please refer to How do I fill out an application?.
Medical Exam
•If a medical exam is necessary, CIC will send you instructions on doing the medical examination.
Security Screening
•If you have a criminal record you may not be allowed to enter Canada. People who pose a risk to Canada’s security are not allowed to come to Canada either. As part of the application process to come to Canada, CIC checks to ensure that applicants do not pose a risk to the safety and security of Canadians.
•You can expect CIC to ask you to provide a police certificate.
Selection Interview or Waiver Decision
•If an interview is necessary, CIC will contact you with an interview date.
•If an interview is not necessary, the application moves to the next step.
Decision
•If CIC approves your application, it will issue the immigration document for which you applied.
•If your application is refused you will be sent a decision letter indicating the reason for the refusal either by mail or e-mail.