Photo posted to Flickr by Skip the Budgie

What is Bollywood? That is popular term used for film industry in Hindi language, which is based in Mumbai (India). It would be incorrect to call whole of Indian cinema with this name, because it is only one of its parts.

Bollywood is one of the largest film-making centers in the world, and also the largest film producer in India. Its name is a blend of old name of Mumbai - Bombay, and the center of the American film industry - Hollywood. More proper name for Bollywood is Hindi cinema, but poetic Urdu words are used pretty often. More frequent use of Indian English in dialogues is noticeable, lots of English words are used, phrases, even whole sentences and songs.

Music used in Bollywood film industry is called filmi music. Songs are usually pre-recorded by professional playback singers, and the actors' role is only to pretend to sing, while often dancing at the same time. Only few of actors are also singers.

The dancing in Hindi films is mostly adaptation of Indian dance, like classical or folk dance styles. The use of Western (MTV like) dance moves is also frequent, making its way along with folk dance. The dancing character is often supported by a group of dancers. One should not be surprised if some unrealistic fight scene is replaced by an attractive concubine-looking girl (tawaif) singing and dancing.
Bollywood producers often remake popular Hollywood films in an Indian context. Framed with low budget, they copy everything they find interesting: plot, story, scenes, music... mixing it altogether in one unique spicy Indian mixture. Consider yourself prepared - being too spicy, it can have the same effect like the curry on the stomach of the foreigner! Watch some examples (gamellama's choice!):

Indian Superman trailer - Superman man of steel

It is part of the real film, and it can be an example of mixture of the Hollywood story and an Indian context. Watch the Indian Superman man of steel and his girl in Spider-woman costume singing, dancing and fighting!

Indian Transformers - Dancing Autobot - dubbed add

Citroen C4 add with dubbed Indian music. Just wander what would Optimus Prime dancing be like?

Indian Simpsons clip - the Singhsons - parody!

The Singhons! - funny Indian version of the Simpsons.

Don't get offended by this examples, modern Bollywood releases are something (completely?) different!