Once a doctor physically exams you, and deems that you meet the criteria for one of the qualifying conditions they may issue a certfication that will allow you to have access to medical marijuana products for up to 210 days. After the 210 days expire the doctor must physically exam you again to re-certify you.
A certification is given to you when the doctor determines you have a qualifying condition. An order is the actual recommendation for medical marijuana, and has a maximum length of 70 days, which can be renewed twice during your 210 day certification. After the 210 days expire the doctor must physically exam you again to re-certify you.