Visitor Visa is a kind of Temporary Resident Visa (TRV), which you may need before entering Canada. Most of the foreign nationals need permission from Canadian Immigration Authorities to travel, visit family and friends, do business, on transit through Canada or visit Canadian Attractions Events etc. like Museums, National Parks, and Canada’s Historic Sites.
So most people need a VISA or an Electronic Travel Authorisation (ETA) to come/travel to Canada, depending upon their nationality and their status in the country, they are coming from. In most cases, these days you need to give your BIOMETRICS.BIOMETRICS include fingerprints and photo.
You can apply for Visitor Visa online or on paper as well.