Persons who are not Canadian residents or Citizens who wish to work, study or simply visit Canada must apply for "Temporary Status" to Citizenship and Immigration Canada. These "visitors" must be granted Visitor visa, or Employment Authorizations if they wish to work temporarily in Canada; or a Student Authorization if they wish to study in Canada.

Citizenship and Immigration Canada will deny entry into Canada to all persons who, in the opinion of the immigration official at the port of entry, do not intend to leave Canada at the expiry of their Visitor status.

Immigration Canada requires that Visitors should not have a criminal record or pose a security risk, should be in good health, and should have sufficient funds to support themselves during their temporary stay in Canada.

Category
Temporary Worker visa
International Student visa 
Visitor Visa

Please also check Changes to Canada's Immigration Act and Regulations