Jungle is usually hip hop beats taken from the mid 80s to the early 90s, and speed up. If you watch that show "In Living Color", that is a prime example of a hip-hop beat with potential to become a jungle beat. To be a jungle beat it must contain many hit-pitch snares, and cymbols, and the occasional bass beat. Jungle usually replaces the bass beats with a bass line.
Not to be confsused with drum n bass which uses bass beats, instead of a large bass line as in jungle.
Why do commercials use jungle? I've noticed a few Lexus ads on TV have used The Prodigy remixed to their liking, its more jungly than the original songs, but I knows its them.