These are 3 different stages that majority of the PR applicants will see against Background check in my CIC.
IP1
--------
IP1 will be shown when we pass the medical. Some people get this update on the same day along with their medical and some of them couple of days after. CIC agents will do R10, criminality checks during this stage. Once they feel everything is good then they will change it to NA. These things will happen at CIO Office (Centralized Intake Office)
NA
---------
This stage, our file will be transferred to CPC (Case processing Center) where agents will do eligibility assessments. If they feel everything is okay, then they will provide their recommendation to Visa Officer and same time they will initiate Security Checks.
IP2
--------
This status will be seen in my CIC account once Visa Officer starts reviewing or after reviewing all agents recommendations. On the same day PPR request will be triggered if the applicant paid RPRF upfront. These things will be done at CPC office.
It is not necessary that every applicant will undergo this process. But majority of the cases, I have noticed the same status.
Hope it helps