Shortly: IP2 - “In progress” 2: Background check changes to “We are processing your background check. We will send you a message if we need more information.”
More details:
Post-submission stages: NA1[/B] - “Not Applicable” 1: Background check says “Not Applicable”, usually right after submission.
MEP - Medicals passed: review of medical results changes from “You do not need a medical exam.” to “You have passed the medical exam.”
IP1 - “In progress” 1: Background check changes to “Your application is in progress. We will send you a message when we start your background check.” Usually follows MEP. Some applicants (especially inland and CEC) skip this stage.
NA2 - “Not Applicable” 2: Background check changes to “Not Applicable” again after IP1. Some applicants skip this stage and it is easily missed.
IP2 - “In progress” 2: Background check changes to “We are processing your background check. We will send you a message if we need more information.”
NA3 - “Not Applicable” 3: Background check changes to “Not Applicable” again after IP2 (uncommon)
Ghost update - When you log in, the application says it’s been “updated” but none of the fields have changed. Often considered a sign that PPR is coming soon. Not seen by all applicants.
PPR - Passport request: IRCC sends “Ready for visa” e-mail asking you to submit your documents to your visa office so they can issue your CoPR and entry visa if applicable.
CoPR - Confirmation of Permanent Residence: A document that says you’ve been approved for permanent residence.
These are not “official” stages, but they are used frequently throughout the forum to track processing of applications.