A Schengen Visa is the document issued by the appropriate authorities to the interested party for visiting/travelling to and within the Schengen Area.
The Schengen Area is comprised of 26 countries that have agreed to allow free movement of their citizens within this area as a single country. Of the 26 countries bound by the Schengen agreement, 22 are part of the EU and the other 4 are part of the European Free Trade Association (EFTA).
Schengen area covers the majority of European countries, except for the United Kingdom and countries such as Romania, Bulgaria, Croatia, Cyprus and Ireland soon to be part of the agreement. However, there are countries that are not part of the EU like Norway, Iceland, Switzerland and Lichtenstein yet do belong in the Schengen area and cherish the free movement policy.
The citizens of the non-Schengen member countries are requested a mandatory Schengen Visa in order to enter the Schengen Zone. There are exceptions to this rule, however: for some countries that are not part of the Schengen Agreement yet aren’t required a visa to enter the Schengen zone.
The list of the countries that need a visa to enter the Schengen Area can be found HERE.
In order to travel to one or more of the Schengen Zone countries, one needs to apply for a Schengen visa at the designated embassy/consulate. There are however, certain requirements similar to every embassy/consulate that have to be met in order to pursuit the application.