The 21 km long street in Manhattan is best known as the location of many New York theatres. In fact, its name often works as a metaphor or a synonym for the theatre (and mainly musical theatre) production in New York.
Interestingly though, there are not many actual theatres located on Broadway as such (there are only 4). Most of the theatres in the area are scattered across the Theatre District surrounding Broadway.
Up to date, the most successful musical to be played on Broadway is The Lion King. The majority of the tickets for Broadway plays are bought by the tourists.
If you are a fan of a performer who performs on Broadway during your visit, you may want to join the stagedooring groups of fans who wait for their idols outside the theatres hoping to get an autograph.