Here is a comprehensive summary of the Wikipedia article on Big Brother 15:

  • Broadcast and Winner: The fifteenth season of the American reality TV series Big Brother premiered on June 26, 2013, on CBS, and concluded after 90 days with a finale on September 18, 2013. Hosted by Julie Chen, the season was won by Andy Herren, who defeated GinaMarie Zimmerman in a 7-2 jury vote, while Elissa Slater was voted America's Favorite HouseGuest.

  • Format and Twist: The season retained the classic format of Head of Household, Power of Veto, and eviction votes, but introduced a major twist: each week, viewers secretly voted for a "Big Brother M.V.P." who could anonymously nominate a third HouseGuest for eviction. In a further twist, during weeks four through six, the public directly chose the third nominee.

  • Jury and Broadcast Changes: A significant rule change increased the jury from seven to nine members, meaning the final nine evicted HouseGuests would decide the winner. This was also the last season to be broadcast in 4:3 standard definition, as all future seasons would be produced in high-definition.