What exactly is the series about? 

A Group of People called 'Housemates' live in a purpose built house over the course of 11- 13 weeks with no contact to the Outside world.Cameras catch their every move and Microphones catch every sound they make. Their is no privacy at all. Each Week. Big Brother sets Housemates tasks in which they compete to gain money to buy Food for the group. Also Housemates are required to Nominate two people each week to place up for Eviction. The people with the most Nominations are placed up for Eviction. At the end of a week, a live show is broadcast and the Housemate with the most votes to be evicted, is Evicted in front of the live crowd nicknamed 'The Eviction Crowd' . In Special cases, Big Brother cancels Nominations. 

This is followed until the final week where their are NO nominations and the public vote for who they want to win. The Winner is revealed in a live show in front of a live crowd. In cases, Big Brother Final's launch other series such as Big Brother 11 saw their final launch Ultimate Big Brother which followed a All-Star format. (Previous Housemates return to the house for another 3 weeks to compete)