A passport is a travel document to certify the identity and nationality of its holder. A visa is a permit for a foreign national to enter or transit a territory.
Generally, a visa is an endorsement in a passport or other travel document functioning as a passport. Visa may also be issued in a separate paper. For example, immigrant visa issued by USA or Canada is a set of document for the holder to carry and be fingerprinted when entering the territory. Singapore may also issue such visa to foreigners. Visa shall be used together with the passport.
Single or multiple entry: There are single-entry visa and multi-entry visa.
Types of visa by purpose: Categories and names of visa may vary from country to country. There are diplomatic visa, official visa, immigrant visa, non-immigrant visa, courtesy visa, tourist visa, work visa, student visa, business visa, dependent visa.
Types of visa by duration: Long-stay visa and short-stay visa. The application for long-stay visa may take a longer time to process regardless what purpose it may be. A visa with duration of stay not longer than 3 months is considered a short-stay visa and its application takes comparatively shorter time.