The overall winner takes home an M9-P and a lens, plus 5,000 Euros – currently around $6,300 USD. Non-professional entrants under the age of 25 can submit to the Newcomer Award. It’s made for aspiring pros and awards the winner an M9-P and lens, but no cash prize.
The Oskar Barnack award is given in honor of Barnack himself, who invented the Leica camera back in 1914. The first award was given out back in 1979, on the 100th anniversary of his birth.
You can find more info about the awards, submitting your photos and a bit of Leica history at the Oskar Barnack Award page.