Your Ontario Health Card is your proof that you are covered by OHIP and should be brought with you every time you visit a medical facility.
To be eligible for OHIP, you must be physically in Ontario for at least 153 days in any 12-month period and make Ontario your primary home. Eligibility is open to Canadian citizens, permanent residents (landed immigrants), those who have applied for permanent residence (who have met the eligibility requirements and have not yet been denied) or who have a valid work permit. There are other eligibility options as well.
To learn more about applying for OHIP and obtaining a Health Card, please visit the OHIP page on the Government of Ontario website.