Traveling in Europe has been simplified with the introduction of the Schengen visa. As a visitor to the Schengen area, you will enjoy the many advantages of this unified visa system.
With a Schengen visa, you may enter one country and travel freely throughout the Schengen zone. Internal border controls have disappeared; there are no or few stops and checks. This means that internal air, road and train travel are handled as domestic trips, similar to travel from one US state to another. Those who traveled in Europe before Schengen know the difference.
For more information on Schengen, click here
http://www.eurovisa.info/SchengenVisa.htm