Industry pertain to Bombay, Bollywood is the name given to the Mumbai-based Hindi-language film industry in India. When combined with other Indian film industries (Tamil, Telugu, Bengali, Malayalam, Kannada), it is considered to be the largest in the world in terms of number of films produced, and maybe also the number of tickets sold.
The term Bollywood was created by conflating Bombay (the city now called Mumbai) and Hollywood (the famous center of the United States film industry).
Bollywood films are usually musicals. Few movies are made without at least one song-and-dance number. Indian audiences expect full value for their money; they want songs and dances, love interest, comedy and dare-devil thrills, all mixed up in a three hour long extravaganza with intermission. Such movies are called masala movies, after the spice mixture masala. Like masala, these movies have everything.
The plots are often melodramatic. They frequently employ formulaic ingredients such as star-cro