The Bollywood film industry is based in the city of Mumbai, which used to be called Bombay (where the ‘Bo’ came from) whereas Hollywood is based in the now widely-recognised movie capital of the world: Hollywood or LA.
Bollywood actually started first in 1899 when the first Indian short film was screened. Hollywood officially started about a decade later (give or take a few years).
As I’ve already mentioned Hollywood is probably more popular and has more money going in, and coming out of it (maybe because ticket prices are higher).
Hollywood movies and stars are also more widely known and recognised, globally than those of Bollywood.
Despite not being as widely known, globally, Bollywood is definitely a massive industry and should not be overlooked. Many stars have made the transition successfully like Priyanka Chopra (now engaged to Nick Jonas, and attended the most recent Royal Wedding).