Visa: A visa is a document issued by a country giving an individual permission to formally request entrance to the country during a given period of time and for certain purposes and usually stamped or glued inside of a passport, or sometimes issued as separate pieces of paper. Many countries require possession of a valid passport and visa as a condition of entry for foreigners, though there exist exemptions.
FOREX (Foreign Exchange Market): The foreign exchange (currency or forex or FX) market exists wherever one currency is traded for another. It is by far the largest financial market in the world, and includes trading between large banks, central banks, currency speculators, multinational corporations, governments, and other financial markets and institutions.