What is the basic difference between Passport & Visa?

A passport is a travel document issued by a national government that usually identifies the bearer as a national of the issuing state and requests that the bearer be permitted to enter and pass through other countries. Passports are connected with the right of legal protection abroad and the right to enter one's country of nationality. Passports usually contain the holder's photograph, signature, date of birth, nationality, and sometimes other means of individual identification. Many countries are in the process of developing biometric properties for their passports in order to further confirm that the person presenting the passport is the legitimate holder. A visa (short for the Latin carta visa, lit. "the document having been seen") is a document issued by a country giving a certain individual permission to formally request entrance to the country during a given period of time and for certain purposes (see below for caveats and exceptions). Most countries require possession of a vali ... more