In Canada, the definition of work for immigration purposes is not based on payment, but how competitive your activities are in the labour market. Volunteer positions, internships, and unpaid work might be considered work, even if you are not paid. For example, if you volunteer for a position that is normally performed by paid employees , such as photocopying or customer service, it is considered working in Canada.
If your volunteer position or internship is considered work, you must have the right work authorization before you start. Unpaid work hours are counted towards the 20 hours per week of off-campus work you may be eligible for as a full-time student.