You can work for the Canadian employer of your choice with the Open Work Permit, excluding:
- ineligible employers (check the list here), or
- employers who provides sex trade related services (escorting, strip tease, erotic massages and dance, etc.).
The Open Work Permit can only be issued in some distinct circumstances, such as if you are a dependent family member of permanent residents, a participant in the Working Holiday of International Experience Canada, a refugee or refugee claimant, applying for the Bridging Open Work Permit, etc. You can find if you are eligible by answering a few questions here.