It means that your sponsor has been approved and your relationship to your sponsor has now been approved. This is known as AIP: Approval in Principle.
Approved in principle / Approval in principle (AIP)
Your application is “approved in principle (AIP)” if:
- you have received a letter from IRCC stating that you meet the permanent residence eligibility requirements, but
- you still have to pass the medical, security and background checks for you and, if needed, your family members.
All that's left is the medical (unless you've had your exam already), background and security checks!
If you want/need an Open Work Permit, you can apply now, but...you may be nearing the finish line for your PR so consider the extra cost of OWP (~$255, unless it's gone up).