Tourist visa: A tourist visa is usually valid for 1 month, allowing single or multiple entry.
Business Visa: A business visa is usually valid for 3 month, allowing single or multiple entry and the right to work. Getting a business visa has now become cheap and easy, although the prices are about double those of a tourist visa. Please see Vietnam visa fees for more information about cost for applying for Vietnam visa online.
Student visa: A student visa is usually arranged after your arrival. It's acceptable to enter Vietnam on a tourist visa, enroll in a Vietnamese language course and then apply at the immigration police for a change in status. In reality, the easiest way to do it is to contact a travel company and have them help you make the application.
Transit visa (or visa for city visiting): The maximum duration of this type of visa is 5 days. The Immigration Department will issue transit visa for groups in tour, accompanied with a tour guide. The group must have exact itinerary and have guarantee of a travel agency which organizing the tour.