As mentioned in Inyo's excellent writeup, bearbagging is used to secure human food while backpacking or camping, since wild animals that have learned to scavenge from human tourists often become a danger to people and consequently themselves. The method described in the previous writeup (equally weighted bags of food and other smellables --- which include sunscreen, toothpaste, and trash, none of which should ever be kept near sleeping areas --- counterbalanced across a tree branch) is better than hanging everything over a branch from one end of a rope and tying the other to the tree. This is because many bears have learned to defeat it by chewing through the rope tied to the tree. In some highly visited areas, such as Yosemite National Park, bears have even learned to defeat counterbalances --- one ranger station has pictures of a mama bear who taught her cubs to climb up on her shoulders to retrieve bear bags. No kidding! In cases such as these, it becomes necessary to employ bear cans and bear boxes to protect your campsite and the bears.