Wall Street is basically the financial district of New York City, named after the street is has centered on.

It is the home of the world's largest stock exchange, New York Stock Exchange. Also several other major exchanges have or had headquarters in the Wall Street area, including NASDAQ, the New York Mercantile Exchange, the New York Board of Trade, and the former American Stock Exchange. The term has become a metonym for the financial markets of the United States and it is one of the world's principal financial centers.

The name of this street was derived from an earthen wall on the northern boundary of the New Amsterdam settlement, perhaps to protect against English colonial encroachment or incursions by native Americans in 17th century.
For a regular tourist there is not really much to see here expect that it is a famous street. Visitors have not been permitted inside the NYSE since September, 2001. However to think that the Federal Reserve gold vaults worth $100 billion are right below the street (in 80 feet) here is pretty surreal.