A visitor visa will allow you to visit Canada with the intention to leave Canada on before the time allowed by CBSA. Canada is very attractive destination for tourists and students and welcomes over 35 million tourists, students, visitors every year. Visit visas are available under three different categories:

Single entry visa:

This allows you to visit Canada only once (unless travelling to the US or St. Pierre and Miquelon) and you can be granted permission to remain in Canada at the port of entry for a maximum period of 6 months only. You can apply to extend your stay in Canada if needed and will need to make an application for extension at least 30 days before expiry.

Multiple entry visa:

This allows you to enter and depart Canada on multiple occasions and is valid for up to 6 months, depending on the issuing case officer. You will need to specify how long you will require your Canadian visitor visa (not exceeding a six month period) and leave it to the case officer to decide if this is necessary.

Transit Visa:

This visa was initially designed for those people entering Canada for a period of 48 hours or less. For example, if your method of transport has to stop in Canada and you are from a country that requires you to have a visa to visit Canada, you will require a transit visa.
You are not permitted to work on any of the above Canadian Tourist Visa categories and some applicants may also need to obtain a Temporary Resident Visa in addition to the above if they come from certain countries. Some basic things to consider before making an application for a Canada Tourist Visa are:
Health issues (you may be required to undergo a medical examination)
Funds to secure your stay
You may need a letter of invitation from a friend of relative currently residing in Canada
You may require a Temporary Resident Visa.

Once you have secured your visit visa then you may also need to obtain a temporary resident visa if you come from certain countries. If you wish to work temporarily in Canada, you can find further information in the Work Permits section.