SINGLE ENTRY VISIT VISA
The single-entry Visa only permits you to visit Canada for a single time. Once you leave Canada, other than to United States and St. Pierre and Miquelon, you will require a new Visa to return to and gain entrance to Canada.
You will not be required to get a new visitor Visa to come back to Canada provided that your visa is still valid and you endeavor to travel only and directly to the United States (including its Territories and Possessions) or St. Pierre and Miquelon, you do not need a new visitor visa to return to Canada.
MULTIPLE ENTRY VISIT VISA
A multiple entry visa enable visitors to enter and leave Canada for six months at a time, without having to reapply each time. It can be valid for up to 10 years, or one month before your passport expires, whichever is earlier. You must leave Canada before the expiry date on your visa. The Multiple-Entry Visitor Visa has become a popular option among visitors from China, India, and Mexico who hold 10-year passports and are eligible to apply for a 10-year visa. Those who are from countries where less than ten-year period valid passport is issued they get a visa as long as their passports are valid.