Big Brother is an all-seeing, all powerful entity in the game. Therefore, Big Brother, in ways, symbolizes God, an omni-present power.
Getting HoH in Big Brother signifies safety and and freedom from eviction. It also symbolizes power, and the Hoh has the obligation to nominate two houseguests for eviction.
The power of veto enabled the winning houseguest to take someone off the nomination block. The veto was more powerful that HoH at times because they could override the nominations and force the HoH to put up a new person. The power of veto symbolizes power, and safety.
The Diary Room is a private room where the houseguests can say whatever they want, and no one else can hear except Big Brother. This room is treated as a confession, like in the Christian religion, and Big Brother would be on par with a priest, listening attentively to the 'confessions'.
Used to bring closure, and represents an end. Much like one's final words before death, since it means an end of their game life.
At the end of each Big Brother eviction night, the houseguests that remain in the house say final words to the departed houseguest. These 'good-bye' messages are recorded before the ousted guest leaves, and before the votes are cast, and are done in private in the Diary Room.
Forming friendships and building alliances, is vital, for one's existing within the game. Alliances within the game can represent alliances of every day life. If one does not make an alliance, then he or she, will undoubtedly be voted out of the game. Examples of strong alliances present in Big Brother are:
Chilltown - Will Kirby and Mike "Boogie" - Both winners of Big Brother. Will in season 2, and Mike in season 7.
The Nerd Herd, or the Friendship - season 6 - produced Maggie Ausburn as the overall winner
The Four Horsemen - Season 5 - produced Drew Daniel as the overall winner