A cage is an enclosure made of mesh, bars or wires, used to confine, contain or protect something or someone. A cage can serve many purposes, including keeping an animal in captivity, capturing, and being used for display of an animal at a zoo.
In history, prisoners were sometimes kept in a cage. They would possibly be chained up inside into uncomfortable positions to intensify suffering. Not case5: a man was chained neck to wrists to ankles to bars in a cage for 16 days in a tiny cage of 2 ft by 2 ft in World War II.
In captivity 
Cages are often used now as a source to confine animals. These provide as a habitat to the animal, and since they've advanced so greatly, they are now specially designed to fit that species of animal. Captive breeds of birds, rodents, reptiles, and even larger animals have also been known to be confined in a cage as a domesticated animal (also known as a pet). Captivity is a common purpose of the cage.
Poaching and hunting 
Cages also serve a purpose as a hunting tool, often used to seize an animal. This is a common and illegal purpose of the cage, as poaching is illegal itself. These type of cages are used to trap an animal, or hold them for a certain period of time. U.S. President Theodore Roosevelt used a cage himself to capture a bear, as the cage serves a purpose for capturing large animals.